Talk:Book - The development of the chick (1919)

THE DEVELOPMENT OF THE CHICK - AN INTRODUCTION TO EMBRYOLOGY BY

FRANK R. LILLIE

PROFESSOR IN THE UNIVERSITY OP CHICAGO

SECOND EDITION, REVISED

NEW YORK HENRY HOLT AND COMPANY

1919

Copyright, 1908, 1919,

BY

HENRY HOLT AND COMPANY

CHAPTER XIII THE URINOGENITAL SYSTEM

The history of the pronephros and the origin of the mesonephros have been ah'eady described (Chap. VI). We have now to consider (1) the later history of the mesonephros, (2) the development of the metanephros or permanent kidney, (3) the development of the reproductive organs and their ducts, and (4) the development of the suprarenals. All these organs form an embryological unit, by virtue of their mode of origin and their interrelations. Thus we find that the intermediate cell-mass is significant for the development of all: its growth causes the formation of the Wolffian body, on the median face of which the gonads arise. The secreting tubules and renal corpuscles of the permanent kidney are also derivatives of the intermediate cell-mass. The Wolffian duct is derived from the same source, and by change of function becomes the vas deferens, after functioning for a while as the excretory duct of the mesonephros. Certain parts of the mesonephros also enter into the construction of the testis. And the Miillerian duct, which forms the oviduct of the female, is derived from the epithelium covering the Wolffian body.

I. The Later History of the Mesonephros In Chapter VI we traced the origin of the nephrogenous tissue, and the differentiation of the first mesonephric tubules within it. We saw that in each of the segments concerned a number of balls of cells arises by condensation within the nephrogenous tissue, and that these become converted into vesicles. We saw also that each vesicle sends out a tubular sprout from its lateral side to the Wolffian duct, with which it unites; and that its median face becomes converted into a renal corpuscle. These processes take place sucessively in antero-posterior order within the somites concerned, so that a series of stages in the development of the tubules may be studied in the same embryo. Moreover, all the tubules of a given somite do not develop simul .378

THE URIXOGEXITAL SYSTEM

379

taneously: primary tubules are formed in each somite from the most ventral portion of the nephrogenous tissue; then secondar}tubules later from an intermediate portion, and tertiary tubules later yet from the dorsal portion.

Fig. 217 represents a transverse section through the middle

^»f^^5^° v'"'it>f ^i:^j#^^'

Fig. 217. — Transverse section through the middle of the

Wolffian body of a chick embryo of 96 hours.

Ao., Aorta. Coel., Coelome. Col. T., Collecting tubule. Glom., Glomerulus, germ. Ep., Germinal epithelium. M's't., Mesentery, n. t., Nephrogenous tissue. T. 1,2, 3, Primary, secondary, and tertiary mesonephric tubules. V. c. p., Posterior cardinal vein. W. D., Wolffian duct.

of the Wolffian body at the stage of ninety-six hours, showing a primary, secondary, and tertiary tubule. The primary tubule is typically differentiated; the secondary has formed the secreting tubule and the rudiment of the renal corpuscle, but the tubule does not yet open into the Wolffian duct, though it is connected with it; the tertiary tubule is still in the vesicular stage. Some undifferentiated nephrogenous tissue remains above the rudiment of the tertiary tubule, which makes it possible that quarternarv tubules mav be formed later.

Referring still to the same figure, it will be noted that the Wolffian duct itself has formed a considerable evagination dorsomedially (collecting tubule), with which both secondary and tertiary tubules are associated as well as the undifferentiated nephrogenous tissue. Similar evaginations are formed along the entire length of the functional portion of the mesonephros.

380

THE DEVELOPxAIEXT OF THE CHICK

0(,

ov

o

Q>(

o

OO,

o

o

o

o r

o

xoz

X22

-2ZIC

22YII

Fig. 114. A.

Figs. 218 and 219 illustrate the form of these evaginations in duck embr3^os of 40 and 50 somites respectively, as they appear in reconstructions of the posterior portion of the mesonephros.

It will be seen that they gradually form sacs opening into the Wolffian duct. Subsequently, by elongating, these sacs form collecting tubules that gather up the secretions of the mesonephric tubules proper and conduct them to the Wolffian duct. These conducting tubules are stated to branch more or less; it is also said that they are more highly developed in the duck than in the chick. Felix proposes to call them mesonephric ureters.

In the case of the secondary and tertiary tubules, three parts may be distinguished : parts one and two (derived from the nephrogenous tissue) I;. o\C ^rc the renal corpuscle and secreting

tubule respectively; the third part is the collecting tubule derived by evagination from the Wolffian duct. In the case of the primary tubules, a conducting part appears to be formed secondarily, though in what way is not clear.

The formation of new tubules ceases on the fifth day, all the nephrogenous tissue being then used up. Up to the eighth day at least the tubules grow rapidly in length and become more differentiated. The result is a relatively enormous protrusion into the bodv-cavity on each side of the dorsal mesentery. Degeneration of the tubules sets in about the tenth or eleventh days, and the tissue is gradually absorbed;

2Mir

'XSKT

THE URIXOGEXITAL SYSTEM

381

this process extends over the whole of the latter period of incubation, and is completed at hatching. Parts, however, remain in the male in connection with the testis; non-functional remnants

O ^ °o o O

O.'l

' ."fi.T •-.

yxxiii

n.T.

Fig. 219. — Profile reconstruction of part of the

mesonephros and diverticulum of the ureter of

a duck embryo of 50 somites. (After Schreiner.)

CI., Cloaca. Int., Intestine. Mn. T., Meso nephric tubules, n. T., Nephrogenous tissue.

Ur Ureter W. D.. Wolffian duct.

XXXII, XXXIII, XXXIV, Somites of the same number.

may also be detected in the female (p. 401). It is difficult to state the exact period of beginning and cessation of function of the mesonephric tubules. Judging from the histological appear

PiG 918 — Profile reconstruction of part of the Wolffian duct and primordia of mesonephric tubules (represented by circles) of a duck embryo of 45 somites. (After Schreiner.) YXTV XXV etc., position of the correspondmg somites. Lines 114 A,

114 B 114 C ^represent the positions of the sections shown in these figures.

382

THE DEVELOPMENT OF THE CHICK

ances, however, it is probable that secretion begins in the tubules on the fifth day and increases in amount up to the eleventh day at least, when signs of degeneration become numerous. Presumably the functional activity diminishes from this stage on, being replaced by the secretion of the permanent kidney.

SrC:^

Gq/?.-%

Fig. 220. — Transverse section through the mesonephros

and neighboring parts of a 6-day chick, in the region of

the spleen.

Ao., Aorta, bl. V., Blood vessels (sinusoids). Caps., Capsule of renal corpuscle. Coel., Coelome. col. T., Collecting tubule. D., Dorsal. Giz., Gizzard. Glom., Glomerulus. Gon., Gonad. L., Left. Spl., Spleen. Sr. C, Cortical substance of the suprarenal, s. t., Secreting tubule. T. R., Tubal rid^e. V., Ventral. V. c. p., Posterior cardinal vein V. s'c. 1., Left subcardinal vein. W. D., Wolffian duct.

Figs. 220 and 221 represent sections through the mesonephros on the sixth and eighth days respectively (see also Fig. 222, eleven days). The renal corpuscles show the typical capsule and glomerulus, and relation to the secreting tubules. The latter are considerably convoluted on the sixth day, much more so on the eighth day. The conducting tubules can usually be distinguished by their smaller caliber and thinner walls. The Wolffian

THE URIXOGEXITAL SYSTEM

383

duct is situated near the dorso-lateral edge of the mesonephros, and the opening of a collecting tubule into it is shown in Figure 220. The renal corpuscles are situated next the median face of the Wolffian body. The space between the tubules is occupied

';7.f.o.z.

Mh'tr

-3.?V iVJ).

apmm

Gon.l

Fig. 221. — Transverse section through the metanephros, mesonephros, gonads and neighboring parts of an 8-day chick, bl. v., Blood vessels (sinusoids). B. W., Body-wall. col. T. M't'n., Collecting tubules of the metanephros. M. D., Miillerian duct. M's't., Mesentery, n. t. i. z., Inner zone of nephrogenous tissue (metanephric). n. t. o. z., Outer zone of the nephrogenous tissue. Symp. Gn., Sympathetic o^anghon of the twenty-first spinal ganglion. V. C, Centrum of vertebra. Other abbreviations as before.

almost entirely by a wide vascular network of sinusoidal character; that is, the endothelial walls of the vessels are moulded directly on the basement membrane of the tubules without any intervening connective tissue. The circulation is described in the chapter on the vascular system.

384 THE DEVELOPMENT OF THE CHICK

II. The Development of the Metaxephros or Permanent

Kidney

The metanephros or permanent kidney supplants the mesonephros in the course of development. It is derived from two distinct embryonic primordial (1) the nephrogenous tissue of the two or three posterior somites of the trunk (31 or 32 to 33), which furnish the material out of which the renal corjxiscles and secreting tubules develop; and (2) a diverticulum of the posterior portion of the Wolffian duct (Fig. 219), which develops by branching into the collecting tubules and definitive ureter. The development of the kidney takes place in a mass of mesenchyme, known as the outer zone of the metanephrogenous tissue, that furnishes the capsule and connective tissue elements of the definitive kidney, in which also the vascular supply is developed (Figs. 221 and 222). The cortical tubules of the kidney are thus derived mainly from the nephrogenous tissue, and the medullary tubules and ureter from the metanephric diverticulum.

Thus the definitive kidney is analogous in mode of development to the mesonephros, and is best interpreted as its serial homologue. This point of view may be regarded as definitely established by the work of Schreiner, to which the reader is referred for a full account of the history of the subject.

The metanephric diverticulum, or primordium of the ureter and collecting tubules, arises about the end of the fourth da}^ as a rather broad diverticulum of the Wolffian duct at the convexity of its terminal bend to the cloaca (Fig. 219). It grows out dorsally, forming a little sac, which, however, soon begins to grow forward median to the posterior cardinal vein and dorsal to the mesonephros (Fig. 224); by the end of the fifth day its anterior end has reached the level of the csecal appendages of the intestine, and on the eighth day its anterior end has reached its definitive position at the level of the vena cava inferior, near to the anterior end of the mesonephros (twenty-first definitive somite or twenty-fifth of the entire series; cf. Fig. 150).

It should be noted that the metanephric diverticulum is similar in its mode of origin to the so-called mesonephric ureters. It may in fact be regarded as the posterior member of this series, but it is separated from those that form the collecting tubules of the mesonephros by at least two somites in which no diverticula

THE URINOGEXITAL SYSTEM

385

of the mesonephros are formed (Fig. 219). During its growth forward a series of small diverticula arise from its wall and extend dorsally (Fig. 223); these branch secondarily in a generally dichot

,'-^i,< ■•'>"!■'■-■<- ■■■■---■: .

Af^Y.

^y^

Fig. 222. -Transverse section through the metanephros, mesonephros gonads and neighboring structures of an 11-day male chick, a. A. S., Abdominal air-.sac. Ao., Aorta B W Rndv wall r^^i n

duct. Mst., .Mesentery. M't'n., Metanephros. Sp., Spine of neural areh

W D^'woMandScrotr' '\t """.'^' "*'. J e.^., Vna ca"™ Meri*: vv . u., \^ oiman duct. Other abbreviations as before.

386

THE DEVELOPMENT OF THE CHICK

Fig. 223. — Profile reconstruction of the Wolffian duct and primordium of the metanephros of a chick embryo of 6 days and 8 hours. (After Schreiner.)

XXV to XXXIH, twentv-fifth to thirty-third somites. Al. N., Neck of allantois. CI., Cloaca. Int., Intestine. M's'n., Mesonephros. n. T., Nephroojenous tissue of the metanephros included within the dotted lines. W. D., Wolffian duct. Ur., Ureter.

THE URIXOGEXITAL SYSTEM 387

omoiis manner, and it is from them that the collecting tubules of the kidney arise; the posterior unbranched portion of the metanephric diverticulum represents the definitive ureter.

The following data concerning these branches should be noted:

(1) the first ones are formed from the posterior portion of the metanephric diverticulum, and the process progresses in an anterior direction. This is the reverse direction of the usual order of embryonic differentiation, but the reason for the order is the same, viz., that differentiation begins in the first formed parts.

(2) A posterior, smaller group of collecting tubules is separated at first by an unbranched portion of the ureter from an anterior larger group (Fig. 223). The unbranched region corresponds to the position of the umbilical arteries which cross here. (3) During the fifth and sixth days the terminal portion of the Wolffian duct common to both mesonephros and metanephros is gradually drawn into the cloaca, and thus the ureter obtains an opening into the cloaca independent of the Wolffian duct and posterior to it (Fig. 223).

The Nephrogenous Tissue of the Metanephros. The nephrogenous tissue of the thirty-first, thirty-second, and thirty-third somites is at first continuous with the mesonephros (Figs. 218 and 219), but on the fourth and fifth da3^s that portion situated immediately behind the mesonephros degenerates, thus leading to a complete separation of the most posterior portion situated in the neighborhood of the metanephric diverticulum. This constitutes the metanephrogenous tissue proper (inner zone). It is important to understand thoroughly its relations to the metanephric diverticulum. This is indicated in Fig. 219, which represents a graphic reconstruction of these parts in a duck embryo of 50 somites. It will be seen that the metanephrogenous tissue covers nearly the entire metanephric diverticulum; a transverse section (Fig. 224) shows that it lies on its median side. The outer dotted line (Fig. 219) gives the contour of a dense portion of mesenchyme related to the diverticulum and nephrogenous tissue proper. In section this forms a rather ill-defined area shading into the nephrogenous tissue on the one hand and into the surrounding mesenchyme on the other.

Fig. 224 shows the relations of the three constituent elements of the kidney at the end of the fifth day, as seen in a transverse section. The metanephric diverticulum lies on the median side

388

THE DEVELOPMENT OF THE CHICK

of the cardinal vein, and is in contact, on its median face, with the proper nephrogenous tissue (inner zone); the latter shades into the outer zone, the cells of which are arranged concentrically with reference to the other parts. The relations subsequently established may be summarized in a few Avords; the inner zone of tissue grows and branches pari passu with the growth and branching of the metanephric diverticulum, so that the termination of every collecting tubule is accompanied by a portion of

Fig. 224. — Transverse section through the

ureter and metanephrogenous tissue of a

5-day chick.

A. umb., Umbilical artery. Coel., Coelome.

M's't., Mesentery, n. t. i. z., Inner zone of the

nephrogenous tissue, n. t. o. z., Outer zone of

the nephrogenous tissue. Ur., Ureter. V. c.p.,

Posterior cardinal vein. W. D., Wolffian duct.

the inner zone, which is, however, always distinct from it. This conclusion is established by the fact that from the start the two elements, collecting tubules and inner zone, are distinct and may be traced continuously through every stage. The outer zone differentiates in advance of the two more essential constituents at all stages, and thus forms a rather thick investment

for them.

The formation of the secreting tubules from the inner zone

THE URIXOGEXITAL SYSTEM

389

Fig. 225. — Sections of the embryonic metanephros of the chick to show developing tubules. (After Schreiner.)

A. Nephric vesicle or primordium of secreting tubule (ur. t ) and collecting tubule (col. T.); 9 days and 4 hours.

B. Elongation of nephric vesicle; same embryo.

C. Indication of renal corpuscle at the distal end of the forming tubule.

D. The secreting tubule appears S-shaped.

E. Secreting tubule well formed; 9 davs and 21 hours.

F. Secreting tubule opening into collecting tubule; 11 days.

390 THE DEVELOPMENT OF THE CHICK

of the metanephrogenous tissue takes place in essentially the same manner as the formation of the mesonephric tubules. The first stages may be found in seven and eight-day chicks in the portion of the kidney behind the umbilical arteries. The inner zone tissue begins to arrange itself in the form of minute balls of cells in immediate contact with the secreting tubules; a small lumen then arises within the ball, transforming it into a thickwalled epithelial vesicle with radially arranged cells. The vesicle then elongates away from the collecting tubule and gradually takes on an S-shape. The distal end of the S becomes converted into a renal corpuscle as illustrated in Figure 225 and the proximal end fuses with the wall of the collecting tubule; an opening is then formed between the two.

On the eleventh day of incubation, secreting tubules are thus formed throughout the entire length of the kidney; but the histological structure does not yet give the effect of an actively secreting gland, although degeneration of the mesonephros has already begun. The full development of the nephric tubules in the chick has not been studied.

At all stages in its develojDment the kidney substance is separated from the mesonephros by a distinct layer of undifferentiated mesenchyme, which is, however, at certain times extremely thin. But there is no evidence that at any time elements of the mesonephros, e.g., undifferentiated nephrogenous tissue, extend up into the metanephric primordium which so closely overlies it (cf. Figs. 221 and 222).

The kidney is entirely retroperitoneal in its formation, and its primary capsule is established by differentiation of the periphery of the outer zone. This may be seen in process at eleven days (Fig. 222) : the primary capsule is definitely estal^lished on its median and lateral sides; but is defective dorsally and at the angle next the aorta. With the subsequent degeneration of the mesonephros, and projection of the kidney into the coelome, its ventral surface acquires a secondary peritoneal capsule.

III. The Organs of Reproduction

The gonads are laid down on the median surface, and the ducts on the lateral surface of the Wolffian body, which thus becomes converted into a urinogenital ridge. The composition of the urinogenital ridge is at first the same in all embryos, whether

THE URIXOGENITAL SYSTEM 391

destined to become male or female. It has three divisions: (1) the anterior or sexual division, containing the gonad, involves about the anterior half of the Wolffian body; (2) a non-sexual region of the Wolffian body occurs behind the gonad, and (3) behind the Wolffian body itself the urinogenital ridge contains only the Wolffian and Mullerian ducts. A transverse section through the anterior division shows the following relations (Fig. 221): on the mecUan surface the gonad, on the lateral surface near the dorsal angle of the body-cavity the Wolffian and Mullerian ducts, the latter external and dorsal to the former: between the gonad and ducts lie the tubules of the Wolffian body destined to degenerate for the most part.

There is an incUfferent stage of the reproductive system during which the sex of the embryo cannot be determined, either bv the structure of the gonad or the degree or mode of development of the ducts. In those embryos that become males the gonad develops into a testis, the Wolffian duct becomes the vas deferens, the tubules of the anterior part of the Wolffian body become the epididymis, those of the non-sexual part degenerate, leaving a rudiment known as the paradidymis, and the Mullerian duct becomes rudimentary or disappears. In embryos that become females, the gonad develops into an ovary; the Wolffian duct disappears or becomes rudimentary, the Mullerian duct develops into the oviduct on the left side and disappears on the right side, and the tubules of the Wolffian body degenerate, excepting that functionless homologues of the epididymis and paradidymis persist, known as the epoophoron and paroophoron respectively.

It is not correct to state, as is sometimes done, that the embryo is primitively hermaphrodite, for, though the ducts characteristic of both sexes develop equally in all embryos, the primitive gonad is, typically, only indifferent. Nevertheless, if the gonad be physiologically as well as morphologically indifferent in its primitive condition, the possibility of an hermaphrodite development is given. The primitive embryonic conditions appear to furnish a basis for any degree of development of the organs of both sexes.

Development of Ovary and Testis. Indifferent Period. The reproductive cells of ovary and testis alike arise from a strip of peritoneal epithelium, known as the germinal epithelium, which is differentiated on the fourth day by its greater thickness

392 THE DEVELOPMENT OF THE CHICK

from the adjacent peritoneum (Fig. 217). The germinal epithelium lies between the base of the mesentery and the mesonephros at first, but as the latter grows and projects into the body-cavity the germinal epithelium is drawn on to its median surface. It is difficult to determine its antero-posterior extent in early stages; it begins near the point of origin of the omphalomesenteric arteries, and its posterior termination is indefinite, but it certainly extends over seven or eight somites.

Two kinds of cells are found in the germinal epithelium, viz., the ordinary peritoneal cells and the primordial germ-cells. The latter are typically round, and several times as large as the peritoneal cells (Figs. 226 and 227); the cytoplasm is clear but contains persistent yolk granules and a large attraction sphere, and the nucleus contains one or two nucleoli; they are sharply distinguishable from the peritoneal cells, and they may be traced through a continuous series of later developmental stages into the ova and spermatozoa. The origin of these primordial germ-cells is therefore a matter of considerable interest.

Two views have been held: (1) that they are derived from the peritoneal cells, and (2) that they have an independent history antecedent to the differentiation of a germinal epithelium, representing in fact undifferentiated embryonic cells that reach the germinal epithelium by migration from their original source. The former view was due to Waldeyer, and was supported by observations of cells intermediate in structure between the primordial germ-cells and cells of the peritoneum (e.g. by Semon). These observations have, however, been shown to be erroneous. The second view has been demonstrated for a considerable number of vertebrates; and quite recently Swift has shown that the primordial germ-cells of the chick arise from the germ-wall at the anterior margin of the pellucid area in a late stage of the primitive streak; that they later enter the blood stream and are carried into the embryo; some, which reach various inappropriate positions, degenerate; but others leaving the blood near the base of the mesentery reach the germinal epithelium by migration. The independent and early origin of germ-cells has an obvious bearing on the theory of the continuity of the germ-plasm of Weismann.

THE URINOGENITAL SYSTEM

393

Two other epithelial constituents enter into the composition of the indifferent gonad, viz.: the rete tissue or cords of the urinogenital union, and the sexual cords. These lie between the germinal epithelium and the glomeruli of the Wolffian body. Between these elements is a sparse mesenchyme continuous with the surrounding mesenchyme, constituting the stroma of the gonad.

.*,^

V

ty.b

• V^

^V^.-_

m

w -*■•« ' * '

'A~s t.

Fig. 226. — Cross-section through the genital primordium of Limosa segocephala. (After Hoffmann, from Fehx and Biihler.)

The stage is similar to that of a chick embryo of 4| days.

Germ., Germinal epithelium. Mst., Mesentery. S. C., Rete cords. v., Posterior cardinal vein. W. D., Wolffian duct.

Some primordial germ-cells occur in the stroma, though most are in the germinal epithelium.

The rete cords appear within the gonad on the fifth day; they are solid cords of epithelial cells that fill up the interior

394 THE DEVELOPMENT OF THE CHICK

of the gonad and cause it to protrude from the surface of the Wolffian body (Fig. 226); the cords extend from the germinal epithelium towards the hilum of the gonad (represented at this time by the broad surface opposed to the Wolffian body), and into the Wolffian body where they enter into close connection with the renal corpuscles. In the Wolffian body and intermediate zone they are very irregular in their course and connected by numerous anastomoses, corresponding to the rete region of the future testis. Strands of these cells pass dorsally, and, according to some authors, form the cortical cords of the suprarenal capsules (Fig. 226).

The following views of the origin of the rete cords in birds have been held: (1) That they arise as outgrowths of the capsules of renal corpuscles (Hoffmann, Semon) and the neck of the Wolffian tubules also (Semon); (2) that they are ingrowths of the germinal epithelium (Janosik); (3) that they differentiate from the stroma (Prenant, Firket). The subject is a somewhat difficult and complicated one, but the view that the rete cords arise as outgrowths of the capsules of renal corpuscles brings the birds into line, in this respect, with the reptiles and amphibia. Hoffmann's observation that the rete cords lie at first on the lateral side of the blood-vessels intervening between the germinal epithelium and the Wolffian body, and that the cells of the cords are directly continuous with those of the capsules, should be conclusive.

The sexual cords arise as proliferations of the germinal epithelium which appear as buds projecting into the stroma (Fig. 227). They are definitely limited in time of origin between the middle of the fifth and sixth days of incubation (Swift). They carry with them numerous primordial germ-cells from the germinal epithelium. About the end of the sixth day all free themselves from the germinal epithelium, and a layer of stroma begins to separate them sharply from the latter. They are destined to form the seminiferous tubules in the male, and the so-called medullary cords in the female.

Sexual Differentiation. The period of morphological indifference of the gonad is relatively long and the actual sexual differentiation appears slowly. It manifests itself (1) in differences in the behavior of the germinal epithelium; (2) of the sexual cords;

THE URINOGENITAL SYSTEM

395

(3) larger size of the left ovary and ultimate disappearance of the right one; (4) behavior of the stroma, particularly the albuginea. The sex of the embryo can first be definitely determined about the 156th hour, by the relative sizes of the two gonads, by the behavior of the germinal epithelium and by the presence of a larger

K,'-^

germ. ep.

pro.

m.

y^^/.

4

coelom

.fSf

Fig. 227. — Portion of a transverse section through an ovary of a 6^ day chick embryo (after Swift), germ, ep., germinal epitheHum. m. c, sexual cord. pr. o., primordial germ-cells.

number of primordial germ-cells in the germinal epithelium of

the female. (Swift.)

As already stated, the sexual cords form the seminiferous tubules of the testis; they are made up of two kinds of cells, viz.: the primordial germ-cells and the ordinary peritoneal cells derived from the germinal epithelium. After the seventh day they constitute most of the bulk of the testis, and the rete cords are pressed towards the hilum by the sexual cords which radiate in that direc

396

THE DEVELOPIMENT OF THE CHICK

tion. The sexual cords now begin to branch and anastomose, and soon form a reticulmn with mesenchyme in the meshes. About the thirteenth day the primordial germ-cells, which have been inactive, begin to divide, and a rapid increase in numbers ensues.

Intc. sir.

> -*=

m^f

'^:y/:

•%

vSJ*;*

?^:

.?*'

?,i'

Fig. 228. — Portion of a transverse section through the right testis of a 20 day chick embryo. The section shows a seminiferous cord in which a lumen is beginning to develop. Note the position and polarization of the spermatogonia (after Swift). Int. c, interstitial cells. L., beginning of lumen. M. C, Mitochondrial granules within a spermatogonium, p. c, supporting cells, derivatives of peritoneal cells of the sexual cords, s. c, seminiferous cord, sp., spermatogonia, str., stroma.

The sexual cords are solid up to about the twentieth day of incubation; a lumen then begins to appear and they become transformed into tubules (Fig. 228). The primordial germ-cells form the spermatogonia, and the peritoneal cells form the supporting cells of the seminiferous tubules (Swift).

After the sixth day the germinal epithelium of the testis rapidly retrogresses and becomes reduced to a thin peritoneal

THE URIXOGENITAL SYSTEM 397

endothelium. The stroma of the primitive testis remains scanty up to the eleventh day. It then increases rapidly between the sexual cords and also forms a layer between germinal epithelium and seminiferous tubules, which becomes the albuginea. Interstitial cells appear in the stroma of the testis about the thirteenth day and increase so rapidly as to form an immense amount by the twentieth day (Swift).

As the testis increases in size it projects more from the surface of the Wolffian body, and folds arise above and below it as well as in front and behind, that progressively narrow the surface of apposition, which in this way becomes gradually reduced to form the hilum of the testis, through which the rete cords pass to the neighboring renal corpuscles (cf. Figs. 221 and

222).

As the testis is attached to the anterior portion of the Wolffian body, the latter may be divided in two portions, an anterior sexual and a posterior non-sexual portion. In the latter part of the period of incubation the non-sexual portion undergoes absorption while the anterior portion becomes converted into the

epididymis.

The irregularly anastomosing rete cords in the region of the hilum are united to the neighboring renal corpuscles by the original strands and these form the vasa efferentia. In order to complete the urinogenital union it is necessary that the rete cords unite with the seminiferous tubules. The exact manner in which this takes place has not been worked out for the chick; but there is no doubt that this union does take place so that the seminiferous tubules connect by way of the rete with the mesonephric tubules and thus with the Wolffian duct.

As regards the formation of the epididymis: the renal corpuscles of the Wolffian tubules concerned diminish in size, the glomerulus disappears and the cells of the capsule become cylindrical. These changes progress from the lateral side of the Wolffian body towards the testis; that is to say, the more lateral corpuscles are first affected. A rudiment of the non-sexual part of the Wolffian body persists in the . mesorchium of the male, between testis and kidney. It is known as the paradidymis.

The development of the ovary in the chick has been studied in recent years by Firket and by Swift.

The right ovary never undergoes much development after

398

THE DEVELOPMENT OF THE CHICK

the indifferent stage; it is destined to retrogress, and finally it disappears.

In the indifferent gonad the sexual cords are formed in the same way whether the organ is to become ovary or testis; but, whereas in the case of the testis these cords are destined to form the functional seminiferous tubules, in the case of the ovary they form only the cords of the medulla. The cortex of the ovary which includes the functional follicles develops from a second

Fig. 229. — Cross-section of the ovary of a young embryo of Numenius arcuatus. (After Hoffmann.) bl. v., Blood-vessel, germ. Ep., Germinal epithelium, r., rete ovarii. s. c, Sexual cord.

proHferation of the germinal epithelium. The sexual cords cease to grow, and become converted into tubes with a wide lumen, and low epithehum; shortly after hatching they entirely disappear.

The characteristic feature of the development of the ovary is a second period of intensive growth of the germinal epithelium accompanied by a rapid increase of the primordial germ-cells contained in it. This goes on very rapidly during the eighth to the eleventh days of incubation. The inner surface of the germinal epithelium, or ovigerous layer of the ovary, begins to form

THE URIXOGEXITAL SYSTEM

399

low irregular projections into the stroma, or the latter begins to penetrate the ovigerous layer at irregular distances so as to produce elevations. This condition is well illustrated in Fig. 229.

In the course of development the ovigerous layer continually increases in thickness, and the projections into the stroma form veritable cords of ovigerous tissue, which correspond to the

i^s^^iS:

^^

Fig. 230. — Cross-section of the ovary of a fledgling of Numenius arcuatus 3-4 days old. The germinal epithelium is below. (After Hoffmann.) s. c, Sexual cords.

cords of Pfltiger in the mammalian ovary. The cords carry the primitive ova with them. The surface of the ovary also begins to become lobulated by the extension of the stroma trabeculae. Successive stages in the growth and differentiation of the primitive ova occur from the surface towards the inner ends of the ovigerous strands. Fig. 230 represents a section through

400 THE DEVELOPIMENT OF THE CHICK

the ovary of a fledgling of Numenius arcuatus three or four days old. The germinal epithelium covers the surface and is continuous with the ovigerous strands projecting far into the stroma. The strands are broken up in the stroma into nests of cells; next the germinal epithelium are found characteristic primitive ova, but in deeper situations the primitive ova are larger and each is accompanied by a group of epithelial cells, which are distinctly differentiated as granulosa cells of young follicles in the deepest. Thus the young follicles arise by separation of nests of cells from the ovigerous strands within the stroma; each nest includes a young ovocyte and a group of epithelial cells which arrange themselves in a single layer of cuboidal cells around the ovocyte. On each side of the free border of the ovary the embryonic state persists, and it is not known whether this condition is maintained permanently, as in some reptiles, or not.

The atrophy of the Wolffian body is much more complete in the female than in the male; no part of it remains in a functional condition, but the part corresponding to the epididymis of the male remains as a rudiment, known as the epoophoron. It has almost the same structure in young females as in young males, but the rete cords uniting it with the ovary do not become tubular. A rudiment of the non-sexual part of the Wolffian body is also found in the hen between ovary and Iddney in the lateral part of the mesovarium; it has been named the paroophoron.

Development of the Genital Ducts. The Wolffian Duct. The origin and connections of the Wolffian ducts have been already sufficiently described. In the male they are connected with the seminiferous tubules by way of the epididymis, vasa efferentia, and rete, and function as vasa deferentia exclusively, after degeneration of the mesonephros. Subsequently they become somewhat convoluted, acquire muscular walls and a slight terminal dilatation. The details of these changes are not described in the literature. In the female the Wolffian duct degenerates; at what time is not stated in the literature, but presumably along with the Wolffian body.

The Mullerian Duct. The Miillerian duct, or oviduct, is laid down symmetrically on both sides in both male and female embryos; subsequently both right and left ]\Iiillerian ducts degenerate in the male; in the female the right duct degenerates, the

THE URIXOGEXITAL SYSTEM 401

left only remaining as the functional oviduct. We have now to consider, therefore, (1) the origin of the ducts during the indifferent stage, and (2) their subsequent history in the male and in the female.

The origin of the IMlillerian duct is preceded by the formation of a strip of thickened peritoneum on the lateral and superior face of the Wolffian body extending all the way to the cloaca (cf. Fig. 220). This strip, which may be called the tubal ridge, appears first at the anterior end of the Wolffian body on the fourth da}", and rapidly differentiates backwards; it lies immediately external to the Wolffian duct. The anterior part of the Miillerian duct arises as a groove-like invagination of the tubal ridge at the cephalic end of the Wolffian body immediately behind the external glomeruli of the pronephros. The hps of this groove then approach and fuse on the fifth day, so as to form a tube which soon separates from the ridge. This process, however, takes place in such a way as to leave the anterior end of the tube open and this constitutes the coelomic aperture of the oviduct, or ostium tuh(£ abdominale. Moreover, the closure of the groove does not take place uniformly, and one or two openings into the Miillerian duct usually occur near the ostium on the fifth clay. Typically, however, these soon close up, though persistence of one of them may lead, as a rather rare abnormality, to the occurrence of two ostia in the adult. There is no ground for the view (see Balfour and Sedgwick) that the two or three openings into the anterior end of the Miillerian duct correspond to nephrostomes of the pronephros; they are situated too far posteriorly and laterally to bear such an interpretation.

The anterior part of the Miillerian duct is thus formed by folding from the epithelium of the tubal ridge; it constitutes a short epithelial tube situated between the Wolffian duct and the tubal ridge, ending blindly behind. The part thus formed is relatively short; the major portion is formed by elongation of the anterior part, which slowly grows backwards between the Wolffian duct and the tubal ridge, reaching the cloaca on the seventh day. The growing point is solid and appears to act like a wedge separating the Wolffian duct and the tubal ridge, being thus closely pressed against both, but apparently without receiving cells from either. Balfour's view, that it grows by splitting off from the Wolffian duct or at the expense of cells contributed by the latter,

402 THE DEVELOPAiEXT OF THE CHICK

has not been supported by subsequent investigators. A short distance in front of the growing point the Mullerian duct receives a kuiien, and mesenchyme presses in from above and below, and forms a tunic of concentrically arranged cells around it

(Fig. 221).

The ]Mullerian duct thus begins to project above the surface of the Wolffian body, and, as it does so, the thickened epithelium of the tubal ridge becomes flat and similar to the adjacent peritoneum; whether it is used up in the formation of the mesenchymatous tunic of the epithelial Mullerian duct is not known. Up to this time the development is similar in both sexes and on both sides of the body.

In the male development of these ducts ceases on the eighth day; retrogression begins immediately and is completed, or at any rate far advanced, on the eleventh day. In this process the epithelial wall disappears first, and its place is taken by cells of mesenchymatous appearance, though it is not known that transformation of one kind into the other takes place. Retrogression begins posteriorly and proceeds in the direction of the head; the ostium is the last to disappear. The mesenchymatous tunic shares in the process, so that the ridge is no longer found (see Fig. 222). In the male the IMullerian ducts never open into

the cloaca.

In the female the development of the right Mullerian duct ceases after the eighth day, and it soon begins to degenerate. Its lumen disappears and it becomes relatively shorter, so that its anterior end appears to slip back along the Wolffian body. On the fifteenth day slight traces remain along its former course and a small cavity in the region of the cloaca. It never obtains an opening into the cloaca (Gasser).

With the degeneration of the anterior end of the Wolffian body the ostium tubse abdominale comes to be attached by a Ugament to the body-wall (Fig. 231); farther back the ligamentous attachment is to the Wolffian body.

The fimbriae begin to develop on the eighth day on both sides in both sexes. It is only in the left oviduct of the female, however, that development proceeds farther, and differentiation into ostium, glandular part, and shell gland takes place. This appears distinctly about the twelfth day. The lower end expands to form the primordium of the shell

THE URIXOGEXITAL SYSTEM

403

gland at this time, but does not open into the cloaca. Indeed, the opening is not established until after the hen is six months old (Gasser.)

Aom

M'cj2

pl.C.r

/iec.p/j.e/iii'

o.r.a

Vcd.l.

Aar.v.c

Fig. 231. — Photograph of a cross-section of an embryo of 8 clays through the

ostia tubae abdominaha.

a. A. S., Xeck of abdominal air-sac. O. T. a., Ostium tubae abdominale. M's't.ac, Accessory mesentery, pi. C. r., 1., Right and left pleural cavities. Rec. pn. ent. r., Right pneumato-enteric recess. V. c. a. 1., Left anterior vena cava. R., rib. Other abbreviations as before.

IV. The Suprarenal Capsules

The suprarenals of the hen are situated medial to the anterior lobe of the kidney, in the neighborhood of the gonad and vena cava inferior. They have a length of about 8-10 mm. The substance consists of two kinds of cords of cells, known respectively as cortical and medullary cords, irregularly intermingled: the so-called cortical cords make up the bulk of the substance, and the medullary cords occur in the meshes of the cortical cords.

404 THE DEVELOPMENT OF THE CHICK

The terminology does not, therefore, describe well the topographical arrangement of the components; it was derived from the condition found in many mammals, the cortical cords of the birds corresponding to the cortical substance, and the medullary cords to the medullary substance of mammals. The medullary cords are often called phseochrome or chromaffin tissue on account of the specific reaction of the constituent cells to chromic acid, and their supposed genetic relation to tissue of similar composition and reaction found in the carotid glands and other organs associated with the sympathetic system.

The embryonic history has been the subject of numerous investigations, and has proved a particularly difficult topic, if we are to judge from the variety of views propounded. Thus for instance it has been maintained at various times: (1) that cortical and medullary cords have a common origin from the mesenchyme; (2) that they have a common origin from the peritoneal epithehum; (3) that the origin of the cortical and medullary cords is absolutely distinct, the former being derived from the sexual cords by way of the capsules of the renal corpuscles and the latter from the sympathetic ganglia; (4) that their origin is distinct, but that the cortical cords are derived from ingrowths of the peritoneum, and the medullary cords from sympathetic ganglia. The first view may be said now to be definitely abandoned, and no one has definitely advocated a common epithehal origin since Janosik (1883). Thus it may be regarded as well estabUshed that the two components have diverse origins, and it seems to the writer that the fourth view above is the best supported. (See Poll and Soulie.) The comparative embryological investigations strongly support this view.

Origin of the Cortical Cords. According to Soulie, the cortical cords arise as proliferations of a special suprarenal zone of the peritoneum adjacent to the anterior and dorsal part of the germinal epithehum. This zone is distinguishable early on the fourth day, and begins about half a millimeter behind the glomeruH of the pronephros, extending about a millimeter in a caudal direction. Proliferations of the peritoneal epithelium are formed in this zone, and soon become detached as groups of epithelial cells lying in the mesenchyme between the anterior end of the Wolffian body and the aorta. Such proliferation con

THE URINOGEXITAL SYSTEM 405

tinues up to about the one hundredth hour or a httle later, and a second stage in the development of the cortical cords then begins: The cords grow rapidly and fill the space on the mediodorsal aspect of the AVolffian body, and then come secondarily into relation with the renal corpuscles of the latter and the sexual cords.

According to Semon and Hoffmann the relation thus established is a primary one, that is to say, that the cortical cords arise from the same outgrowths of the capsules of the renal corpuscles that furnish the sexual cords. Rabl agrees essentially with Soulie, and it seems probable that Semon and Hoffmann have overlooked the first stages in the origin of the cortical cords of the suprarenal corpuscles.

During the fifth, sixth, and seventh days there is a very rapid increase of the cortical cords accompanied by a definite circumscription of the organ from the surrounding mesenchyme; however, no capsule is formed yet. The topography of the organ on the eighth day is shown in Figs. 150 and 182. Whereas during the fourth, fifth, and sixth days the arrangement of the cortical cells is in masses rather than in cords, on the eighth day the cords are well developed, in form cylindrical with radiating cells, but no central lumen. The organ has become vascular, and the vessels have the form of sinusoids, i.e., they are moulded on the surface of the cords with no intervening mesenchyme.

Origin of the Medullary Cords. The medullary cords take their origin unquestionably from cells of the sympathetic nervous system. During the growth of the latter towards the mesentery, groups of sympathetic cells are early established on or near the dorso-median surface of the cortical cords (Fig. 226). The ingrowth of the sympathetic medullary cords does not, however, begin until about the eighth day. At this time there is a large sympathetic ganglionic mass on the dorso-median surface of the anterior end of the suprarenal, and strands of cells characterized sharply by their large vesicular nuclei and granular contents can be traced from the ganglion into the superficial part of the suprarenal. These cells are precisely like the specific cells of the ganglion, perhaps a little smaller, and without axones. On the eleventh day these strands have penetrated through a full third of the thickness of the suprarenal, and are still sharply characterized, on the one hand by their resemblance to the

406 THE DEVELOPMENT OF THE CHICK

sympathetic ganglion cells, and on the other by their clear differentiation from the cells of the cortical cords. These occupy the relations characteristic of the differentiated medullary cords, and there can be httle doubt that they develop into them.

CHAPTER XIV THE SKELETON

I. General

From an embryological point of view, tlie bones of the body, their associated cartilages, the ligaments that unite them together in various ways, and the joints should be considered together, as they have a common origin from certain aggregations of mesenchyme. The main source of the latter is the series of sclerotomes, but most of the bones of the skull are derived from the unsegmented cephalic mesenchyme.

Most of the bones of the body pass through three stages in their embryonic development: (1) a membranous or prechondral stage, (2) a cartilaginous stage, (3) the stage of ossification. Such bones are known as cartilage bones, for the reason that they are preformed in cartilage. Many (see p. 433 for list) of the bones of the skull, the clavicles and the uncinate processes of the ribs do not pass through the stage of cartilage, but ossification takes place directly in the membrane; these are known as membrane or covering bones. The ontogenetic stages of bone formation parallel the phylogenetic stages, membrane preceding cartilage, and the latter preceding bone in the taxonomic series. Thus, in Amphioxus, the skeleton (excluding the notochord) is membranous; in the lamprey eel it is partly membranous and partly cartilaginous; in the selachia it is mainly cartilaginous; in higher forms bone replaces cartilage to a greater or less degree. The comparative study of membrane bones indicates that they were primitively of dermal origin, and only secondarily grafted on to the underlying cartilage to strengthen it. Thus the cartilage bones belong to an older category than the membrane bones.

The so-called membranous or prechondral stage of the skeleton is characterized simply by condensation of the mesenchyme. Such condensations arise at various times and places described

407

408 THE DEVELOPMENT OF THE CHICK

beyond, and they often represent the primordia of several future bony elements. In such an area the cells are more closely aggregated, the intercellular spaces are therefore smaller, and the area stains more deeply than the surrounding mesenchyme. There are, of course, stages of condensation in each case, from the first vague and undefined areas shading off into the indifferent mesenchyme, up to the time of cartilage or bone formation, when the area is usually well defined. In most of the bones, however, the process is not uniform in all parts; the growing extremities may be in a membranous condition while cartilage formation is found in intermediate locations and ossification has begun in the original center of formation; so that all three stages may be found in the primordium of a single bone {e.g., scapula). Usually, however, the entire element is converted into cartilage before ossification begins.

The formation of cartilage (chondrification) is brought about by the secretion of a homogeneous matrix of a quite special character, which accumulates in the intercellular spaces, and thus gradually separates the cells; and the latter become enclosed in separate cavities of the matrix; when they multiply, new deposits of matrix form between the daughter cells and separate them. As the original membranous primordium becomes converted into cartilage, the superficial cells flatten over the surface of the cartilage and form a membrane, the perichondrium, which becomes the periosteum when ossification takes place.

The process of ossification in the long bones involves the following stages in the chick:

(1) Formation of Perichondral Bone. The perichondrium deposits a layer of bone on the surface of the cartilage near its center, thus forming a bony ring, which gradually lengthens into a hollow cylinder by extending towards the ends of the cartilage. This stage is well illustrated in Fig. 231 A and in the long bones of Fig. 242; the bones of the wing and leg furnish particularly good examples; the perichondral bone is naturally thickest in the center of the shaft and thins towards the extremity of the

cartilages.

(2) Absorption of Cartilage. The matrix softens in the center of the shaft and becomes mucous, thus liberating the cartilage cells and transforming the cartilage into the fundamental tissue of the bone marrow. This begins about the tenth

THE SKELETON

409

day in the femur of the chick. The process extends towards the ends, and faster at the periphery of the cartilage {i.e., next to the perichondral bone) than in the center. In this way there remain two terminal, cone-shaped cartilages, and the ends of the cones project into the marrow cavity (Fig. 231 A).

(3) Calcification of Cartilage. Salts of lime are deposited in the matrix of the cartilage at

the ends of the marrow cavity; such cartilage is then removed by osteoclasts, large multinucleated cells, of vascular endothelial origin, according to Brachet (seventeenth or eighteenth day of incubation).

(4) Endochondral Ossification. Osteoblasts within the marrow cavity deposit bone on the surface of the rays of calcified cartilage that remain between the places eaten out by osteoclasts, and on the irmer surface of the perichondral bone.

These processes gradually extend towards the ends of the bone, and there is never any independent epiphysial center of ossification in long bones of birds, as there is in mammals. The ends of the bones remain cartilaginous and provide for growth in length. Growth in diameter of the bones takes place from the periosteum, and is accompanied by enlargement of the marrow cavity, owing to simultaneous absorption of the bone from within. It is thus obvious that all of the endochondral bone is removed from the shaft in course of time; some remains in the spongy ends.

The details of the process of ossification will not be described here, and it only remains to emphasize a few points. At a stage shortly after the beginning of absorption of the cartilage in the

Fig. 231 A. — Longitudinal section of the femur of a chick of 196 hours' incubation; semi-diagrammatic. (After Brachet.)

art. Cart., Articular cartilage. C. C, Calcified cartilage, end. B., Endochondral bone. M., Marrow cavity. P'ch., Perichondrium. P'os., Periosteum, p'os. B., Periosteal bone. Z. Gr., Zone of growth. Z. Pr., Zone of proliferation. Z. R., Zone of resorption.

410 THE DEVELOPMENT OF THE CHICK

center of the shaft, the perichondral bone is invaded by capillary vessels and connective tissue that break through into the cavity formed by absorption; it is supposed by many that osteoblasts from the periosteum penetrate at the same time. The marrow of birds is derived, according to the best accounts, from the original cartilage cells, which form the fundamental substance, together with the intrusive blood-vessels and mesenchyme. The endochondral osteoblasts are believed by some to be of endochondral origin (i.e., derived from cartilage cells), by others of periosteal origin. For birds, the former view seems to be the best supported.

In birds, calcification does not precede absorption of the cartilage, as it does in mammals, until the greater part of the marrow cavity is formed. The cones of cartilage, referred to above, that are continuous with the articular cartilages, are absorbed about ten days after hatching.

On the whole, perichondral ossification plays a more extensive role in birds than in mammals. The endochondral bone formation begins relatively much later and is less extensive. The bodies of the vertebrae, which ossify almost exclusively in an endochondral fashion, form the main exception to this rule.

Ossification in membrane proceeds from bony spicules deposited between the cells in the formative center of any given membrane bone. It spreads out from the center, the bony spicules forming a network of extreme delicacy and beauty. After a certain stage, the membrane bounding the surface becomes a periosteum which deposits bone in dense layers. Thus a membrane bone consists of superficial layers of dense bone, enclosing a spongy plate that represents the primitive bone before the establishment of the periosteum.

The formation of bones proceeds from definite centers in all three stages of their formation; thus we have centers of membrane formation, centers of chondrification and centers of ossification. Membranous centers expand by peripheral growth, cartilage centers expand by the extension of cartilage formation in the membrane from the original center of chondrification, and bony centers expand in the original cartilage or membrane. Several centers of chondrification may arise in a single primitive membranous center; for instance, in the membranous stage, the skeleton of the fore-limb and pectoral girdle is absolutely con

THE SKELETON 411

tinuoiis; cartilage centers then arise separately in different parts for each of the bones: similarly for the hind-limbs and pelvic girdle, etc. Separate centers of ossification may likewise appear in a continuous embryonic cartilage, as for instance, in the base of the skull or in the cartilaginous coraco-scapula, or ischioilium. Such centers may become separate bones or they may subsequently fuse together. In the latter case, they may represent bones that were phylogenetically perfectly distinct elements, as for instance, the prootic, epiotic, and opisthotic centers in the cartilaginous otic capsule; or they may be of purely functional significance, as for instance, the separate ossifications in the sternum of birds, or the epiphysial and diaphysial ossifications of the long bones of mammals. It is usually possible on the basis of comparative anatomy to distinguish these two categories of ossification centers.

Phylogenetic reduction of the skeleton is also usually indicated in some manner in the embryonic history. Where elements have completely disappeared in the ph3dogenic history, as for instance, the missing digits of birds, they often appear as membrane formations in the embrvo, which then fade out without reaching the stage of cartilage; if the latter stage is reached the element usually fuses with some other and is therefore not really missing, e.g., elements of the carpus and tarsus of birds (though not all). But the ontogenetic reduction may go so far that the missing elements are never distinguishable at any stage of the embryonic history; thus, though the missing digits of birds are indicated in the membranous stage, their component phalanges are not indicated at all.

II. The Vertebral Column

The primordia of the vertebral column are the notochord and sclerotomes. The former is the primitive axial support of the body, both ontogenetically and phylogenetically. In both components, notochord and sclerotomes, we may recognize a cephalic and trunk portion. The notochord, as we have seen, extends far into the head, and the sclerotomes of the first four somites contribute to the formation of the occipital portion of the skull. The cephalic parts are dealt with in the development of the skull. The history of the notochord and sclerotomes will be considered together, but we may note in advance that the

412 THE DEVELOPMENT OF THE CHICK

notochord is destined to be completely replaced by the bodies of the vertebrae, derived from the sclerotomes.

The Sclerotomes and Vertebral Segmentation. The vertebral segmentation does not agree with the primitive divisions of the somites, but alternates with it; or in other words, the centers of the vertebrae do not coincide with the centers of the original somites, but with the intersomitic septa in which the segmental arteries run. Thus each myotome extends over half of two vertebral segments, and the spinal ganglia and nerves tend to alternate with the vertebrae. It therefore happens that each myotome exerts traction on two vertebrae, obviously an advantageous arrangement, and the spinal nerves lie opposite the intervertebral foramina.

This arrangement is brought about by the development of each vertebra from the caudal half of one sclerotome and the cephalic half of the sclerotome immediately behind; parts of two somites enter into the composition of each vertebra, as is very obvious at an early stage: Fig. 232 represents a section through the base of the tail of a chick embryo of ninety-six hours; it is approximately frontal, but is inclined ventro-dorsally from behind forwards. The original somites are indicated by the myotomes and the segmental arteries. In the region of the notochord one can plainly distinguish three parts to each sclerotome, viz., (1) a narrow, median, or perichordal part abutting on the notochord, in which no cUvisions occur either within or between somites; (2) a caudal lateral cUvision distinguished by the denser aggregation of the cells from (3) the cephalic division. Between the caudal and cephalic cUvisions of the sclerotome is a fissure (intervertebral fissure) which marks the boundary of the future vertebrae. Each vertebra in fact arises from the caudal component of one sclerotome and the cephalic component of the sclerotome immediately behind. Between adjacent sclerotomes is the intersomitic septum containing the segmental artery. If one follows these conditions back into successively earlier stages, one finds that the intervertebral fissure arises from the primitive somitic cavity, and that the distinction between caudal and cephalic divisions of the sclerotome is marked continuously from a very early stage by the presence of the intervertebral fissure and the greater density of the caudal division, i.e., the cephalic component of each definitive vertebra.

THE SKELETOX

413

TT — ^5 — a « "o-w

'1 •^^•^-'o.ool

^/7 — ^ ^ifflii'

^

.«"»

, < r. ■,■

CdUd^C/ "^dl "■'5-S:^;

/y7/i:/^

7^^?l?

'»2g.' «>5.<' '• ^- .

.. °SS-,.

1 vs^-i.^-"^'":^^^-^^

5 'D

o v.

4^

■^s

y;7/j. /--^ XtCf"^ -fi-.sV^ -o. o " :

■'-r-,'fc'-V' •'»'£;'■■'/<' '?<^ Co"© ^ -^ .li-a - - S.Jo

^ 6

~ ^ Ask ' S»Jo - , ^»

TK^r^

. .0^:^

^ «. . ', >^.-".,^e

«,,?rV.?:

^!.

"-J

Fig. 232.— Frontal section through the base of the tail of a chick embryo of 96 hours. The anterior end of the section (above in the figure) is at a higher plane than the posterior end. caud. Scl., Caudal division of the sclerotome, ceph Scl Cephalic division of the sclerotome. Derm., Dermatome. Ep., Epidermis. Gn., Ganglion, int's. F., Intersomitic fissure int'v F Intervertebral fissure. My., Mvotome. N'ch., Notochord Nt' Neural tube, per'ch. Sh., Perichordal sheath, s. A., Segmental artery.

414 THE DEVELOPMENT OF THE CHICK

Now, if one follows these components as they appear at successively higher levels in such a frontal section as Fig. 232, one finds that the perichordal layer disappears in the region of the neural tube, and that the spinal ganglia appear in the cephalic division of the sclerotome, and almost completely replace it. Thus the caudal division of the sclerotome is more extensive, as well as denser, than the cephalic division.

In transverse sections one finds that the sclerotomic mesenchyme spreads towards the middle line and tends to fill all the interspaces between the notochord and neural tube, on the one hand, and the myotomes on the other. But there is no time at which the sclerotome tissue of successive somites forms a continuous unsegmented mass in which the vertebral segmentation appears secondarily, as maintained by Froriep, except in the thin perichordal layer; on the contrary, successive sclerotomes and vertebral components may be continuously distinguished, except in the perichordal layer; and the fusion of caudal and cephalic sclerotome halves to form single vertebrae may be continuously followed. Thus, although the segmentation of the vertebrae is with reference to the myotomes and ganglia, it is dependent upon separation of original sclerotome halves, and not secondarily produced in a continuous mass.

Summarizing the conditions at ninety-six hours, we may say that the vertebrae are represented by a continuous perichordal layer of rather loose mesenchvme and two mesenchvmatous arches in each segment, that ascend from the perichordal layer to the sides of the neural tube; in each segment the upper part of the cephalic sclerotomic arch is occupied almost completely by the spinal ganglion, but the caudal arch ascends higher, though not to the dorsal edge of the neural tube. The cranial and caudal arches of any segment represent halves of contiguous, not of the same, definitive vertebra.

Membranous Stage of the Vertebrae. In the following or membranous stage, the definitive segmentation of the vertebrae is established, and the principal parts are laid down in the membrane. These processes are essentially the same in all the vertebrae, and the order of development is in the usual anteroposterior direction. As regards the establishment of the vertebral segments: Figs. 233 and 234 represent frontal sections through the same vertebral primordia at different levels from

THE SKELETON

415

the thoracic region of a five-day chick. The notochord is slightly constricted intervertebrally, and the position of the intersegmental artery, of the myotomes and nerves, shows that each vertebral segment is made up of two components representing succeeding sclerotomes. In the region of the neural arches (Fig. 234) the line of union of cranial and caudal vertebral components is indicated by a slight external indentation at the place of union, and by the arrangement of the nuclei on each side of the plane of union.

Cduc/.Sc/ ceph.Sc'.

//

• » ." '5',*' 'Ir "-V^ ^i*^-^-* -'.

^^V:. .

Mj/-"^^^

ceph Sci.- ^

^ \ . o c

y^i-

.y.y^;{^^> -jt^.> " /^^.^

Fig. 233. — Frontal section through the notochord and pri mordia of two vertebrae of a 5-day chick; thoracic region.

Note intervertebral constrictions of the notochord. The

anterior end of the section is above.

N., Spinal nerve. Symp., Part of sympathetic cord. v. C, Region of pleurocentrum, in which the formation of cartilage

has hegun.

Other abbreviations as in Fig. 232.

The parts of the vertebrae formed in the membranous stage are as follows: (1) The vertebral body is formed by tissue of both vertebral components that grows around the perichordal sheath; (2) a membranous process (neural arch) extends from the vertebral body dorsally at the sides of the neural canal; but the right and left arches do not yet unite dorsally; (3) a lateral or costal process extends out laterally and caudally (Fig. 233) from the vertebral body between the successive myotomes.

The union of the right and left cephalic vertebral components

416

THE DEVELOPMENT OF THE CHICK

(caudal sclerotome halves) beneath the notochorcl is known as the subnotochordal bar (Froriep). It forms earlier than the remainder of the body of the vertebra and during the membranous stage is thicker, thus forming a ventral projection at the cephalic end of the vertebral body that is very conspicuous (Fig. 235).

caud-Se/.

caud Se/

s.A cep/?.'5c/

cac/f^ ^C/

jtfy:

i A^.V

to ei\--^^ i-

»",-^* •c,-^

>p.

S-li

Fig. 234. — Frontal section including the same vertebral primordia as Fig. 233, at a higher level through the neural arches, a. C, Anterior commissure of the spinal cord. v. R., Ventral root of spinal nerve. Other abbreviations as before (Fig;. 232).

It chondrifies separately from the vertebral body and earlier. Except in the case of the first vertebra it fuses subsequently with the remainder of the vertebral body, and disappears as

THE SKELETOX

417

a separate component. Schauinsland has interpreted it as the homologue of the haemal arches of reptilia {e.g., Sphenodon).

The membrane represents not only the future bony parts but the ligaments and periosteum as well. Hence we find that the successive membranous vertebrae are not separate structures but are united by membrane, i.e., condensed mesenchyme, and are distinguishable from the future ligaments at first only by greater condensation. In the stage of Fig. 233, chondrification has already begun in the vertebral body, hence there is a sharp

/v'a

Fig. 235. — Median sagittal section of the cervical region at

the end of the sixth day of incubation. (After Froriep.) x 40.

b. C, Basis cranii. iV. L. 1, 2, 3, First, second, and third intervertebral ligaments, s. n. b. 1, 2, 3, 4, First, second, third, and fourth subnotochordal bars (hypocentra). v. C. 3, 4, Pleurocentra of third and fourth vertebrae.

distinction in this region l^etween the vertebral bod}^ and intervertebral discs. The centers of chondrification, however, grade into the membranous costal processes and neural arches.

The vertebral segmentation has now become predominant as contrasted with the primitive somitic.

The development of the vertebrae during the fifth day comprises: (1) Fusion of successive caudal and cephalic divisions of

418 THE DEVELOPMENT OF THE CHICK

the sclerotomes to form the definitive vertebrae; (2) union of the cephaUc vertebral components beneath the notochord to form the subnotochordal bar; (3) origin of the membranous vertebral bodies and of the neural arch and costal processes.

Chondrification, or development of cartilage, sets in from the following centers in each vertebra: (1) the cephalic neural arches and subnotochordal bar, forming a horseshoe-shaped cartilage at the cephalic end of each vertebra; (2) and (3) right and left centers in the body of each vertebra behind the subnotochordal bar, which soon fuse around the notochord; (the subnotochordal bar probably corresponds to the hypocentrum, and the lateral centers (2 and 3) to the pleurocentra of palaeontologists) ; (4) and (5) centers in each costal process (Figs. 235 and 236). These centers are at first separated by membrane, l)ut except in the case of the costal processes, which form the ribs, the cartilage centers flow together. The neural arches end in membrane which gradually extends dcrsally around the upper part of the neural tube, finally uniting above with the corresponding arches of the other side to form the memhrana reuniens. The chondrification follows the extension of the membrane. During this time the transverse processes of the neural arch and the zygopophyses are likewise formed as extensions of the membrane.

The distinction that some authors make between a primary vertebral l^ody formed ]:)y chondrification within the perichordal sheath, and a secondary vertebral body formed by the basal ends of the arches surrounding the primary, is not a clear one in the case of the chick.

On the seventh and eighth days the process of chondrification extends into all parts of the vertebra; the entire vertebra is, in fact, laid down in cartilage on the eighth da}', although the neural spine is somewhat membranous. Fig. 237 shows the right side of four trunk vertebrae of an eight-day chick, prepared according to the methylene b,lue method of Van Wijhe. The

Fig. 236. — Frontal section of the vertebral column and neighboring structures of a 6-day chick. Upper thoracic region. Note separate centers of chondrification of the neural arch, centrum, and costal processes. Anterior end of section above. B. n. A., Base of neural arch. br. N. 1, 2, 3, First, second, and third brachial nerves. Cp. R., Capitulum of rib. iv. D., Intervertebral disc. Mu., Muscles. N. A., Neural arch. T. R., Tuberculum of rib. V. C, Centrum of vertebra. Other abbreviations as before.

THE SKELETON

419

--jV.D.

420

THE DEVELOPMENT OF THE CHICK

notochord runs continuously through the centra of the four vertebrae shown. It is constricted intra vertebrally and expanded intervertebrally, so that the vertebral bodies are amphicoelous. The intervertebral discs are not shown. A pre- and postzygapophysis is formed on each arch. It is by no means certain that the parts separated by the clear streak shown in the figure extending through centra and arches correspond to the sclerotomal components of the primitive vertebrae, though this was the interpretation of Schauinsland as shown in the figure; further study seems necessary to determine the exact relations of the primitive sclerotomal components to the parts of the definitive vertebra. The successive vertebrae have persistent membranous

Fig. 237. — The right side of four bisected vertebrse of the trunk

of an 8-day chick. (After Schauinsland.)

caud. V. A., Caudal division of vertebral arch. ceph. v. A., Cephalic division of vertebral arch. N'ch., Xotochord.

connections in the regions of the neural spines, zygapophyses and centra. These are shown in Figs. 238 and 239 (cf. also Fig. 150) ; they are continuous with the perichondrium and all are derived from unchondrified parts of the original membranous vertebrae.

Atlas and Axis (epistropheus). The first and second vertebrae agree with the others in the membranous stage. But, when chondrification sets in, the hypochordal bar of the first vertebra does not fuse with the body, but remains separate and forms its floor (Figs. 238 and 239). The body of the first vertebra chondrifies separately and is attached by membrane to the anterior end of the body of the second vertebra, representing in fact the odontoid process of the latter. It has later a separate center of ossification, but fuses subsequently wdth the body of the second vertebra, forming the odondoid process (Fig. 240).

THE SKELETON

421

Formation of Vertebral Articulations. In the course of development the intervertebral discs differentiate into a peripheral intervertebral ligament and a central suspensory ligament which at first contains remains of the notochord. There is a synovial cavity between the intervertebral and suspensory ligaments. This differentiation takes place by a process of loosening and resorption

Fig. 238. — Median sagittal section of the basis

cranii and first three vertebral centra of an

8-day chick.

B. C, Basi-cranial cartilage, iv. D. 1, 2, 3, 4,

First, second, third, and fourth intervertebral

discs. N. T., Floor of neural tube. s. n. b. 1, 2,

First and second subnotochordal bars. V. C.

1, 2, 3, First, second, and third pleurocentra.

of cells just external to the perichordal sheath (Fig. 241). The intervertebral ligament takes the form of paired, fibrous menisci, or, in other words, the intervertebral ligaments are incomplete around the bodies of the vertebrae dorsally and ventrally (Schwarck). Ossification is well advanced in the clavicles, long bones,

422

THE DEVELOPMENT OF THE CHICK

and membrane bones of the skull before it begins in the vertebrae. It takes place in antero-posterior order, so that a series of stages may be followed in a single embryo (cf. Fig. 242). There are three main centers for each vertebra, viz., one in the body and one in each neural arch. The ossification of the centrum is almost

—Medobl

H'9^1112

.f

'." " ">• '•'ti't-'

oC-l.o

-^mk

T/ltl rceiMS.

, i: f 'j'f' , ., f , n yc

■yj

.-^,4^V^J^/?^.^^

UJ:

5p.G/i2-Fi

^■>'i

'RVd.

-+,-'

'-■'oi-.S'"'- (,.'■>•,'■ I ■

5i/mp.Cn

-r/^V4

PiQ 239. — Lateral sagittal section of the same vertebrse (as in Fig.

238). At 1, 2, Floor and roof of atlas. B. C, Basis cranii. Cerv. n. 1, 2, First and second cervical nerves. Med. Obi., Medulla oblongata. R. V. 2, 3, 4, Ribs of the second, third, and fourth vertebrse. V . A. 2, 3, Arches of the second and third vertebrse. XII 2, Second root of hypoglossus.

entirely endochondral, though traces of perichondral ossification may be found on the ventral and dorsal surfaces of each centrum before the endochondral ossification sets in. The perichondral centers soon cease activity. The endochondral centers arise just outside the perichordal sheath near the center of each vertebra on each side of the middle line, but soon fuse around the

THE SKELETON

423

notochord, and rapidly spread in all directions, but particularly towards the surface, leaving cartilaginous ends (Fig. 241). The notochord is gradually reduced and exhibits two constrictions

Fig. 240. — The first cervical vertebrae of a young

embryo of Haliplana fuliginosa. (After Schauins land.)

s.n.b. 1,2, First and second subnotochordal bars. R. 3, 4, 5, 6, Ribs of the third, fourth, fifth, and sixth cervical vertebrae.

and three enlargements within each centrum. The main enlargement occupies the center and the two smaller swellings the cartilaginous ends, the constriction occurring at the junction of the ossified areas and cartilaginous ends (Fig. 241).

J

Fig. 241. — Section through the body of a cervical vertebra of a chick embryo of about 12 days. (After Schwarck.)

1, Endochondral ossification. 2, Articular cartilages. 3, Notochord. 4, Loosening of cells of the intervertebral disc, forming a synovial cavity. 5, Periosteum. 6, Ligamentum suspensorium surrounding the notochord.

424 THE DEVELOPMENT OF THE CHICK

The centers of ossification in the neural arches arise from tlie perichondrium a short distance above the body of the vertebra, and form bony rings about the cartilaginous arch. They gradually extend into all the processes of the neural arch. Thus the neural arches are separated from the vertebral centra by a disc of cartilage which is, however, finally ossified, fusing the arches and centra. At what time this occurs, and at what time endochondral ossification begins in the arches, is not known exactly for the chick.

The vertebral column of birds is characterized by an extensive secondary process of coalescence of vertebrae. Thus the two original sacral vertebra? coalesce with a considerable number of vertebrae, both in front and behind, to form an extensive basis of support for the long iliac bones. The definitive sacrum may be divided into an intermediate primary portion composed of two vertebrge, an anterior lumbar portion, and a posterior caudal portion. The development of these fusions has not been, apparently, worked out in detail for the chick. The bony centers are all separate on the sixteenth day of incubation (cf. Fig. 249). Similarly, the terminal caudal vertebrae fuse to form the so-called pygostyle, which furnishes a basis of support for the tail feathers.

III. Development of the Ribs and Sternal Apparatus In the membranous stage of the vertebral column, all of the trunk vertebra? possess membranous costal processes the subsequent history of which is different in different regions. In the cervical region these remain relatively short, and subsequently acquire independent centers of chondrification and ossification. The last two cervical ribs, however, acquire considerable length. In the region of the thorax, the membranous costal processes grow ventralward between the successive myotomes and finally unite in the formation of the sternum (q.v.). In the lumbar and sacral regions the membranous costal processes remain short. The primary costal process is an outgrowth of the membranous centrum, corresponding in position to the capitulum of the definitive ril). The tuberculum arises from the primary costal process while the latter is still in the membranous condition and grows dorsal ward to unite with the neural arch in the region of the transverse process. (See Fig. 236.)

The centers of chondrification and ossification of the typical

THE SKELETON 425

ribs (cervical and thoracic) arise a short distance lateral to the vertebral centers, with which they are connected only by the intervening membrane, which forms the vertebro-costal ligaments. Chondrification then proceeds distally.

The cervical ribs chondrify from a single center. The thoracic ribs have two centers of chondrification; a proximal one, corresponding to the vertebral division of the rib. and a distal one corresponding to the sternal division. The lumbar and sacral membranous costal processes do not chondrify separately from the vertebral bodies; if they persist at all, therefore, they appear as processes of the vertebrae, and are not considered further.

In the fowl the atlas does not bear ribs, and in the embryo the primary costal processes of this vertebra do not chondrify. The second to the fourteenth vertebrae bear short ribs, with capitulum and tuberculum bounding the vertebrarterial canal. The fourteenth is the shortest of the cervical series. The fifteenth and sixteenth vertebrae bear relatively long ribs, but, as these do not reach the sternum, they are classed as cervical. The entire embryonic history, however, puts them in the same class as the following sternal ribs; on an embryological basis they should be classed as incomplete thoracic ribs. They possess no sternal division, but the posterior one has an uncinate process like the true thoracal ribs. The following five pairs of ribs (vertebrae 17-21) possess vertebral and sternal portions, but the last one fails to reach the sternal rib in front of it.

The vertebral and sternal portions of the true thoracal ribs meet at about a right angle in a membranous joint. This bend is indicated in the membranous stage of the ribs.

The membranous ribs growing downwards and backwards in the wall of the thorax make a sudden bend forward, and their distal extremities fuse (seven and eight days) in a common membranous expansion (primordium of the sternum), which, however, is separated from the corresponding expansion of the opposite side bv a considerable area of the body-wall.

The vertebral and sternal portions of the ribs ossify separately; the ossification of the ribs is exclusively perichondral up to at least the sixteenth day (cf. Fig. 242).

The uncinate processes were not formed in any of the embryos studied. Apparently they arise as separate membranous ossifications after hatching.

The sternum takes its origin from a pair of membranous expan

426

THE DEVELOPMENT OF THE CHICK

sions formed by the fusion of the distal ends of the first four true thoracal ribs; the fifth pair of thoracal ribs does not take part in the formation of the sternum. The sternum thus arises as two distinct halves, which lie at first in the wall of the thorax at the posterior end of the pericardial cavity (eight days). The greatest extension of the sternal primordia is do rso- ventral, the

Fig. 242. — Photograph of the skeleton of a 13-day chick embryo. Prepared by the potash method. (Preparation and photograph by Roy L. Moodie.) 1, Premaxilla. 2, NasaL 3, lachrymaL 4, Parasphenoid. 5, Frontal. 6, Squamosal. 7, Parietal. 8, Exoccipital. 9, Cervical rib. 10, Coracoid. 11, Scapula. 12, Humerus. 13, Ilium. 14, Ischium. 15, Pubis. 16, Metatarsus. 17, Tibiofibula. 18, Palatine. 19, Jugal. 20, Maxilla. 21, Clavicle.

ventral extremities corresponding to the anterior end of the definitive sternum, which is formed by concrescence of the lateral halves in the middle line beginning at the anterior end. The concrescence

THE SKELETON 427

then proceeds posteriorly, as the dorsal ends of the priraordia rotate backwards and downwards towards the middle line.

Although there are two lateral centers of chondrification, these soon fuse. The carina arises as a median projection very soon after concrescence in any region, and progresses backwards, rapidly following the concrescence. There is, therefore, no stage in which the entire sternum of the chick is ratite, though this condition exists immediately after concrescence in any region. The various outgrowths of the sternum (episternal process, anterolateral and abdominal processes), arise as processes of the membranous sternum and do not appear to have independent centers of chondrification.

The sternum ossifies from five centers, viz., a median anterior center and paired centers in the antero-lateral and abdominal processes. The last appear about the seventeenth day of incubation. On the nineteenth day a point of ossification appears at the base of the anterior end of the keel. At hatching centers also appear in the antero-lateral processes. The centers gradually extend, but do not completely fuse together until about the third month. The posterior end of the median division of the sternum remains cartilaginous for a much longer period. In the duck and many other birds there are only two lateral centers of ossification; the existence of five centers in the chick is, therefore, probably not a primitive condition.

IV. Development of the Skull

The skull arises in adaptation to the component organs of the head, viz., the brain, the sense organs (nose, eye, and ear) and cephalic visceral organs (oral cavity and pharynx); it thus consists primarily of a case for the brain, capsules for the sense organs, and skeletal bars developed in connection with the margins of the mouth and the visceral arches. In the chick, the primordia of the auditory and olfactory capsules are continuous ab initio with the primordial cranium; the protecting coat of the eye (sclera) never forms part of the skull. Therefore, we may consider the development of the skull in two sections, first the dorsal division associated with brain and sense organs (neurocranium), and second, the visceral division or splanchnocranium. Although the investment of the eyes forms no part of the skull, yet the eyes exert an immense effect on the form of the skull.

428 THE DEVELOPMENT OF THE CHICK

Development of the Cartilaginous or Primordial Cranium.

(1) The Neurocranium. The neurocranium is derived from the mesenchyme of the head, the origin of which has been described previously. The mesenchyme gradually increases in amount and forms a complete investment for the internal organs of the head. It is not all destined, however, to take part in the formation of the skeleton, for the most external portion forms the derma and subdermal tissue; and, internal to the skeletogenous layer, the membranes of the brain and of the auditory labyrinth, etc., are formed from the same mesenchyme.

The notochord extends forward in the head to the hypophysis (Figs. 67, 88, etc.), and furnishes a basis for division of the neurocranium into chordal and prechordal regions. Within the chordal division again, we may distinguish pre-otic, otic, and post-otic regions according as they are placed in front of, around, or behind the auditory sac. The part of the postotic region behind the vagus nerve is the only part of the neurocranium that is primarily segmental in origin. The sclerotomes of the first four somites (Figs. 63 and 117) form this part of the skull; and at least three neural arches, homodynamous with the vertebral arches, are formed in an early stage, but fuse together while still membranous, leaving only the two pairs of foramina of the twelfth cranial nerve as evidence of the former segmentation. It is also stated that membranous costal processes are found in connection with these arches, but they soon disappear without

chondrifying.

The primordial neurocranium is performed in cartilage and corresponds morphologically to the cranium of cartilaginous fishes. However, it never forms a complete investment of the brain; except in the region of the tectum synoticum it is wide open dorsally and laterally. It is subsequently replaced by bone to a very great extent, and is completed and reinforced by numerous membrane bones.

The neurocranium takes its origin from two quite distinct primordia situated below the brain, viz., the parachordals and the trabecular. The former develop on each side of and around the notochord, being situated, therefore, behind the cranial flexure and beneath the mid- and hind-brain; the trabeculae are prechordal in position, being situated beneath the twixt-brain and cerebral hemispheres, and extending forward through the

THE SKELETON 429

interorbital region to the olfactory sacs. It is obvious, therefore, that the parachordals and trabeculse must form with relation to one another the angle defined by the cranial flexure.

The parachordals appear in fishes as paired structures on either side of the notochord, uniting secondarily around the latter; but in the chick the perichordal portion is formed at the same time as the thicker lateral portions, so that the parachordals exist in the form of an unpaired basilar plate from the first. The trabeculae are at first paired (in the earliest membranous condition), but soon fuse in front, while the posterior ends form a pair of curved limbs (fenestra hypophyseos) that surrounds the infundibulum and hypophysis, and joins the basilar plate behind the latter. At the same time that the parachordals and trabeculae are formed by condensations of mesenchyme, the latter condenses also around the auditory sacs and olfactory pits in direct continuity with the parachordals and trabeculae respectively; so that the auditory and olfactory capsules are in direct continuity with the base of the neurocranium from the beginning.

Chondrification begins in the primordial cranium about the sixth day; it appears first near the middle line on each side, and extends out laterally. Somewhat distinct centers corresponding to the occipital sclerotomes may be found in some birds, but they soon run together, and the entire neurocranium forms a continuous mass of cartilage (sixth, seventh, and eighth days).

During this process the trabecular region increases greatly in length simultaneouslv with the outgrowth of the facial region, and the angle defined by the cranial flexure becomes thus apparently reduced. The posterior border of the fenestra hypophyseos marks the boundary between the basilar plate and trabecular region.

In the region of the basilar plate the following changes take place: (1) in the post-otic or occipital region a dorso-lateral extension (Fig. 244) fuses with the hinder portion of the otic capsule, thus defining an opening that leads from the region of the cavity of the middle ear into the cranial cavity (fissure metotica). This expansion is pierced by the foramina of the ninth tenth and eleventh nerves. (2) The otic region becomes greatly expanded by the enlargement of the membranous labyrinth. The cochlear process grows ventrally and towards the middle line and thus invades the original parachordal region (Fig. 168). The

430 THE DEVELOPMENT OF THE CHICK

posterior region of the otic capsule expands dorsally above the hind-brain, and forms a bridge of cartilage extending from one capsule to the other, known as the tectum synoticum (Fig. 244, 33). (3) The preotic region expands laterally and dorsally in the form of a wide plate (alisphenoidal plate) which is expanded transversely, and thus possesses an anterior face bounding the orbit posteriorly and a posterior face forming part of the anterior wall of the cranial cavity. This plate arises first between the ophthalmic and maxillo-mandibular branches of the trigeminus, and subsequently sends a process over the latter that fuses with the anterior face of the otic capsule, thus establishing the foramen prooticum.

For an account of numerous lesser changes, the student is referred to Gaupp (1905), and the special literature (especially Parker, 1869). The various foramina for the fifth to the twelfth cranial nerves are defined during the process of chondrification ; the majority of these are shown in the figures.

The trabecular region may be divided into interorbital and ethmoidal (nasal) regions. The basis of the skeleton in this region is formed by the trabecule alread}^ described. The median plate formed by fusion of the trabeculse extends from the pituitary space (fenestra hypophyseos) to the tip of the head; a high median keel-like plate develops in the interorbital and internasal regions

Fig. 243. — Skull of an embryo of 65 mm. length; right side. Membrane bones in yellow. Cartilage in blue. (Drawn from the model of W. Tonkoff ; made by Ziegler.)

Fig. 244. — View of the base of the same model.

24.3-244. — 1, Squamosum. 2, Parietale. 3, Capsula auditiva. 4, Capsula auditiva (cochlear part). 5, Fissura metotica. 6, Epibranchial cartilage. 7, Sphenolateral plate. 8, Foramen prooticum. 9, Columella. 10. Otic process of quadratum. 11, Basitemporal (postero-lateral part of the parasphenoid). 12, Articular end of Meckel's cartilage. 13, Angulare. 14, Supra-angulare. 15, Dentale. 16, Skeleton of tongue. 17, Pterygoid. 18, Palatine. 19, Rostrum of parasphenoid. 20, Quadrato-jugal. 21, Jugal (zygomaticum). 22, Vomer. 23, Maxilla. 24, Premaxilla. 25, Anterior turbinal. 26, Posterior turbinal. 27, Nasale. 28, Prefrontal (lachrymale). 29, Antorbital plate. 30, Interorbital foramen. 31, Interorbital septum. 32,Frontale. 33, Tectum synoticum. 34, Foramen magnum. 35, Prenasal cartilage. 36, Orbital process of quadrate. 37, Articular process of Quadrate. 38. Fenestra basicranialis posterior. 39, Chorda. IX, Foramen glossopharyngei. X, Foramen vagi. XII, Foramina hypoglossei.

Fig. 245. — Visceral skeleton of the same model.

1, Dentale. 2, Operculare. 3, Angulare. 4, Supra-angulare. 5. Meckel's cartilage. 6, Entoglossum (cerato-hyal). 7, Copula (1). 8, Pharyngobranchial (1). 9, Epibranchial. 10, Copula (2),

3?

30

3^y

f/g 243

f/"g t45

T,^

a4^

THE SKELETON 431

and fuses with the trabeculse, forming the septum interorbitale and septum nasi (Fig. 243). The free posterior border of this plate hes in front of the optic nerves; an interorbital aperture arises in tlie plate secondarily (Fig. 243).

In the ethmoidal region the septum nasi arises as an anterior continuation of the interorbital plate; and the trabecular plate is continued forward as a prenasal cartilage in front of the olfactory sacs. Curved, or more or less rolled, plates of cartilage develop in the axis of the superior, middle, and inferior turbinals (see olfactory organ), and these are continuous with the lateral wall of the olfactory capsules, which in its turn arises from the dorsal border of the septum nasi (Figs. 243 and 244).

(2) The Origin of the Visceral Chondrocranium (Cartilaginous Splanchnocranium) . The visceral portion of the cartilaginous skull arises primarily in connection with the arches that bound the cephalic portion of the alimentary tract, viz., oral cavity and pharynx. In the chick, cartilaginous bars are formed in the mandibular arch, hyoid arch, and third visceral arch. In fishes, the posterior visceral arches also have an axial skeleton, but hi the chick the mesenchyme of these arches does not develop to the stage of cartilage formation. The elements of these arches are primarily quite distinct. The upper ends of the mandibular and hyoid skeletal arches are attached to the skull; and the lower ends of the three arches concerned meet in the middle line. Two medial elements or copulse are formed in the floor of the throat, one behind the angle of the hyoid arch, and one behind the third visceral arch (Fig. 245).

Mandibular Arch. Two skeletal elements arise in the mandibular arch on each side, a proximal one (the palato-quadrate) and a distal one (Meckel's cartilage). The former is relatively compressed, and the latter an elongated element (Fig. 243, 10). The palato-quadrate lies external to the antero-vertral part of the auchtory capsule, and soon develops a triradiate form. The processes are: the processus oticus, which applies itself to the auditory capsule, the processus articidaris, which furnishes the articulation for the lower jaw, and the processus orhitalis, Avhich is directed anteromedially towards the orbit. A small nodule of cartilage of unknown significance lies above the junction of the processus oticus and otic labyrinth. Meckel's cartilage is the primary skeleton of the lower jaw, corresponding

432 THE DEVELOPMENT OF THE CHICK

to the definitive lower jaw of selachians. It consists of two rods of cartilage in the rami of the mandibular arch, which articulate proximally with the processus articularis of the palatoquadrate cartilage,, and meet distally at the symphysis of the lower jaw. The form of the articulation of the lower jaw is early defined in the cartilage (seven to eight days).

Hyoid Arch. The skeletal elements of the hyoid arch consist of proximal and distal pieces (with reference to the neurocranium) which have no connection at any time. The former are destined to form the columella, and the latter parts of the hyoid apparatus. The columella apparently includes two elements (in Tinnunculus according to Suschkin, quoted from Gaupp) : a dorsal element, interpreted as hyomandibular, in contact with the wall of the otic capsule, and a small element (stylohyal) beneath the former. The two elements fuse to form the columella, the upper end of which is shown in Fig. 168. The stapedial plate (operculum of the columella) is stated to arise in Tinnunculus from the wall of the otic capsule, being cut out by circular cartilage resorption and fused to the columella.

The distal elements of the hyoid arch consist of (1) a pair of ceratohyals, which subsequently fuse in the middle line to form the entoglossal cartilage, the proximal ends remaining free as the lesser cornua of the hyoid, and (2) a median unpaired piece (copula I or basihyal) behind the united ceratohyals (Fig. 245).

First Branchial Arch. The skeletal elements of the third visceral (first branchial) arch are much more extensive than those of the hyoid arch. They are laid down as paired cerato- and epi-branchial cartilages on each side, and an unpaired copula II (basibranchial I) in the floor of the pharynx, in the angle of the other elements (Fig. 245). The cerato- and epibranchials increase greatly in length, and form the long curved elements (greater cornua) of the hyoid, which attain an extraordinary development in many birds.

Ossification of the Skull. The bones of the skull are of two kinds as to origin: (1) those that arise in the primordial cranium, and thus replace cartilage (cartilage bones or replacement bones), and (2) those that arise by direct ossification of membrane (membrane or covering bones).

The cartilage bones of the bird's skull are: (a) in the occipital region; the basioccipital, two exoccipitals, and the supraoccipitals; {h) in the otic region: prootic, epiotic, and opisthotic;

THE SKELETON 433

(c) in the orbital region: the basisphenoid, the orbitosphenoids, the ahsphenoids and ossifications of the interorbital septum; (d) in the ethmoidal region the bony ethmoidal skeleton; (e) the palatoquadrate cartilage furnishes the quadrate bone; (/) a proximal ossification, the articulare, arises in Meckel's cartilage and fuses later with membrane bones; (g) the upper part of the hyoid arch furnishes the columella, and the ceratohyals the os entoglossum; (h) the cerato- and epibranchials ossify independently, as also do the two copulse. (See Figs. 243, 244 and 245.)

The membrane bones of the skull are: (a) in the region of the cranium proper: parietals, frontals, squamosals; (6) in the facial region: lachrymals, nasals, premaxillae, maxillae, jugals, quadrato-jugals, pterygoids, palatines, parasphenoid, and vomer; (c) surrounding Meckel's' cartilage and forming the lower jaw: angulare, supra-angulare, operculare, and dentale. (See Figs. 243, 244 and 245.)

The embryonic bird's skull is characterized by a wealth of distinct bones that is absolutely reptilian; but in the course of development these fuse together so completely that it is only in the facial and visceral regions that the sutures can be distinguished readily.

In order of development the membrane bones precede the cartilage bones, though the latter are phylogenetically the older. Thus, about the end of the ninth day, the following bones are present in the form of delicate reticulated bars and plates: all four bones of the mandible, the faint outline of the premaxillae, the central part of the maxillae, the jugal and quadratojugal, the nasals, the palatines and pterygoids. The base of the squamosal is also indicated by a small triangular plate ending superiorly in branching trabeculae, delicate as frost-work. A faint band of perichondral bone is beginning to appear around the otic process of the quadrate, the first of the cartilage bones to show any trace of ossification. These ossifications appear practically simultaneously as shown by the examination of the earlier stages.

On the twelfth day these areas have expanded considerably, and the frontals and prefrontals (lachrymals) are formed; the rostrum of the parasphenoid is also laid down, and the exoccipitals appear in the cartilage at the sides of the foramen magnum. The parietals appear behind the squamosal (Fig. 242) about the thirteenth day; the basioccipitals soon after. The supraoc

434 THE DEVELOPMENT OF THE CHICK

cipital appears as a pair of ossifications in the tectum synoticum on each side of the dorsal middle line, subsequently fusing together.

A detailed history of the mode of ossification of all the various bones of the skull would be out of place in this book. The figures illustrate some points not described in the text. The reader is referred to W. K. Parker (1869) and to Gaupp (1905).

V. Appendicular Skeleton

The appendicular skeleton includes the skeleton of the limbs and of the girdles that unite the limbs to the axial skeleton. The fore and hind-limbs, being essentially homonymous structures, exhibit many resemblances in their development.

The Fore-limb. The pectoral girdle and skeleton of the wing develop from the mesenchyme that occupies the axis and base of the w^ng-bud, as it exists on the fourth day of incubation. It is probably of sclerotomic origin, but it is not known exactly how many somites are concerned in the chick, nor which ones. After the wing has gained considerable length (fifth day) it can be seen from the innervation that three somites are principally involved in the wing proper, viz., the fourteenth, fifteenth, and sixteenth of the trunk. But it is probable that the mesenchyme of the base of the wing-bud, from which the pectoral girdle is formed, is derived from a larger number of somites.

It is important, then, to note first of all that the scapula, coracoid, clavicle, humerus, and distal skeletal elements of the wing are represented on the fourth day by a single condensation of mesenchyme, which corresponds essentially to the glenoid region of the definitive skeleton. From this common mass a projection grows out distally in the axis of the wing-bud, and three projections proximally in different directions in the bodywall. These projections are (1) the primordium of the wingskeleton, (2) of the scapula, (3) of the coracoid, (4) of the clavicle.

The Pectoral Girdle. The elements of the pectoral girdle are thus outgrowths of a common mass of mesenchyme. The scapula process grows backward dorsal to the ribs; the coracoid process grows ventralward and slightly posterior towards the primordium of the sternum, thus forming an angle slightly less than a right angle with the scapular process; and the clavicular process grows

THE SKELETON 435

out in front of the coracoid process ventrally and towards the middle hne. ThevSe processes are quite well developed on the fifth day, and increase considerably in length on the sixth day, when the hind end of the scapula nearly reaches the anterior end of the ilium, and the lower end of the coracoid is very close to the sternum. The elements are still continuous in the glenoid region.

About the end of the sixth day independent centers of chondrification appear in the scapula and coracoid respectively near their imion; these spread distally and fuse centrally, so that on the seventh day the coraco-scapula is a single bent cartilaginous element. In the angle of the bend, however (the future coraco-scapular joint), the cartilage is in a less advanced condition than in the bodies of the two elements. The clavicular process, on the other hand, never shows any trace of cartilage formation, either in early or more advanced stages, but ossifies directly from the membrane. It separates from the other elements of the pectoral girdle, though not completel}', on the eighth dav.

The scapula and coracoid ossify in a perichondral fashion, beginning on the twelfth da}^, from independent centers, which approach but never fuse, leaving a permanent cartilaginous connection (Fig. 242). The clavicle, on the other hand, is a purely membrane bone; bony deposit begins in the axis of the membranous rods on the eighth or ninth days, soon forming fretted rods that approach in the mid-ventral line by enlarged ends, which fuse directly without the intervention of any median element about the twelfth to thirteenth day, thus forming the furcula or wish-bone (Fig. 246).

The nature of the clavicle in birds has been the subject of a sharp difference of opinion. On the one hand, it has been maintained that it is double in its origin, consisting of a cartilaginous axis (procoracoid) on which a true membrane bone is secondarily grafted (Gegenbaur, Fiirbringer, Parker, and others) ; on the other hand, all cartilaginous preformation in its origin has been denied by Rathke, Goette, and Kulczycki. After careful examination of series of sections in all critical stages, and of preparations made by the potash method, I feel certain that in the chick at least there is no cartilaginous preformation. It is still possible (indeed probable on the basis of comparative anatomy) that the theory of its double origin is correct phylogenetically; but it is certain that the

436

THE DEVELOPMENT OF THE CHICK

procoracoid component does not develop beyond the membranous stage in the chick. It is interesting that the clavicle is the first center of ossification in the body, though perichondral ossification of some of the long bones begins almost as soon.

The Wing-bones. The primordium of the wing-bones is found in the axial mesenchyme of the wing-bud, which is originally continuous with the primordium of the pectoral girdle, and shows no trace of the future elements of the skeleton. The differentiation of the elements accompanies in general the external differentiation of the wing illustrated in Figs. 121 to 124, Chapter VII. The humerus, radius, and ulna arise by membranous differentiation in the mesenchyme in substantially their definitive relations; they pass through a complete cartilaginous stage and

Fig. 246. — Photograph of the pectoral girdle of a chick embryo of 274 hours; prepared by the potash method. (Preparation and photograph by Roy L. Moodie.)

1, Coracoid. 2, Clavicle. 3, Scapula. 4, Humerus.

then ossify in a perichondral fashion (see Fig. 242). In the carpus, metacarpus, and phalanges, more elements are formed in the membrane and cartilage than persist in the adult. Elimination as well as fusion takes place. These parts will therefore require separate description.

As birds have descended from pentadactyl ancestors with subsequent reduction of carpus, metacarpus, and phalanges, it is naturally of considerable interest to learn how much of the ancestral history is preserved in the embryology. The hand is represented in the embryo of six days by the spatulate extremity of the fore-limb, which includes the elements of carpus, metacarpus, and phalanges. From this expansion five digital rays grow out simultaneously, the first and fifth being relatively

THE SKELETOX

437

small; the second, third, and fourth represent the persistent digits. In each ray is a membranous skeletal element, which, however, soon disappears in the first and fifth. Thus there are distinct indications of a i^entadactyl stage in the development of the bird's wing.

In the definitive skeleton there are but two carpal bones, viz., a radiale at the extremity of the radius, and an ulnare at the extremity of the ulna. In the embryo there is evidence of seven transitory pieces in the carpus arranged in two rows, proximal and distal (Fig. 247). In the proximal row only two car

M.c.J

M c. 2

^A*"?^

jPcA

-U

M'c.-?^

Cp.^ Cp3 ^•^■

P'c/).

Fig. 247. — Skeleton of the wing of a chick embryo of 8 days. (After W.

K. Parker.)

Cp. 2, 3, and 4, Second, third, and fourth carpalia. C. U., Centraloiilnare. H., Humerus. I. R., Intermedio-radiale. M'c. 2, 3, 4, Second, third, and fourth metacarpalia. P'ch., Perichondral bone R., Radius. U., Ulna.

tilages appear, viz., the radiale and ulnare; but in earlier stages each appears to be derived from two centers: the radiale from a radiale s.s. and an intermedium, the ulnare from an ulnare s.s. and a centrale. Evidence of such double origin of each is found also in the cartilaginous condition {v. Parker, 1888). Four elements in all enter into the composition of this proximal row. In the distal row there are three distinct elements corresponding to the three persistent digits, and representing, therefore, carpalia II, III, and IV. These subsequently fuse with one another, and with the heads of the metacarpals to produce the carpometacarpus.

On the seventh day the metacarpus is represented Ijy three cartilages corresponding to the three persistent digits, viz., II,

438 THE DEVELOPMENT OF THE CHICK

III, IV. Metacarpal II is only about one third the length of III. Metacarpal IV is much more slender than III, and is bowed out in the middle, meeting III at both ends. The elements are at first distinct, but II and III fuse at their proximal ends in the process of ossification. Cartilaginous rudiments of metacarpals I and V have also been found by Parker, Rosenberg, and Leighton. As to the phalanges, Parker finds two cartilages in II, three in III, and two in IV on the seventh day; but already on the eighth day the distal phalanges of III and I^' have fused with the next proximal one.

As regards the homology of the digits of the wing, the author has adopted the views of Owen, Mehnert, Norsa, and Leighton, that they represent numbers II, III, and IV, which seem to be better supported by the embryological evidence than the view of ^Meckel, Gegenbauer, Parker, and others, that they represent I, II, and HI.

The Skeleton of the Hind-limb. The skeleton of the hindlimb and pelvic girdle develops from a continuous mass of mesenchyme situated at the base of the leg-bud. The original center of the mass represents the acetabular region; it grows out in four processes: (1) a lateral projection in the axis of the leg-bud, the primordium of the leg-skeleton proper, (2) a dorsal process, the primordium of the ilium; and two diverging ventral processes, one in front of the acetabulum (3) the pubis, and one behind (4) the ischium. In the membranous condition the elements are continuous. The definitive elements develop either as separate cartilao-e centers in the common mass (usually), or as separate centers of ossification in a common cartilaginous mass (ilium

and ischium).

The Pelvic Girdle. The primitive relations of the elements of the pelvic girdle in Larus ridibundus is shown in Fig. 248, which represents a section in the sagittal plane of the body, and thus does not necessarily show the full extent of any of the cartilaginous elements, but only their general relations. The head of the femur is seen in the acetabulum, the broad plate of the ilium above and the pubis and ischium as cartilaginous rods of almost equal width below, the pubis in front and the ischiimi behind the acetabuhmi. In this stage the pehdc girdle, in this and many other species of birds, consists of three separate elements on each side in essentially reptilian relations.

THE SKELETOX

439

In the chick at a corresponding age the ihum is much more extensive, and the ischium is united with it by cartilage- the pubis, however, has only a membranous connection with the ilium (contra Johnson). In the course of development the distal ends of the ischium and pubis rotate backwards until the two elements come to lie substantially parallel to the ilium (Figs. 242 and 249). The displacement of the ischium and pubis may

//.

u^

'^lx'~^^'~^i

/s.n.

Is.

Cr.N.

oi.JV.

Fig. 248. — Sagittal section of the right half of the body of Lams ridibundus, to show the composition of the pelvic girdle; x 35. Length of the leg-bud of the embryo, 0.4 mm. (After Mehnert.) F., Femur, cr. N., Crural nerve. II., Ihum. I. s., Ischium. Is. N., Ischial nerve, ob. N., Obturator nerve. P., Pubis.

be associated wdth the upright gait of birds; it is fully established on the eighth day in the chick. The mode of ossification, which is perichondral, is shown in Fig. 249.

Later, the ilium obtains a very extensive pre- and postacetabular union with the vertebrae. I have fomid no evidence in a complete series of preparations (potash) of attachment by ribs arising as indei^endent ossifications. The ischium also fuses

440

THE DEVELOPMENT OF THE CHICK

with the ventral posterior border of the iUum, and the pubis,

except at its anterior and posterior ends, with the free border

of the ischium.

The spina iliaca, a pre-acetabular, bony process of the ihum,

requires special mention inasmuch as it has been interpreted (by Marsh) as the true pubis of birds, and the element ordinarily named the pubis as homologous to the post-pubis of some reptiles. There is no evidence for this in the development. The spina iliaca develops as a cartilaginous outgrowth of the ilium and ossifies from the latter, not from an independent center (Mehnert).

The Leg-skeleton. The skeleton of the leg develops from the axial mesenchyme, which is at first continuous with the primordium of the pelvic girdle. In the process of chondrification it segments into a larger number of elements than found in the adult, some of which are suppressed and others fuse together. The digits grow out from the palate-like expansion of the primitive limb in the same fashion as in the wing. In general the

separate elements arise in the proximo-distal order (Figs. 242 and

249)..

The femur requires no special description; ossification begins

on the ninth day.

The primordium of the fibula is from the first more slender than that of the tibia, though relatively far larger than the adult

Fig. 249. — Photograph of the skeleton

of the leg of a chick embryo of 15 days'

incubation. Prepared by the potash

method. (Preparation and photograph

by Roy L. Moodie.)

1, Tibia. 2, Fibula. 3, Patella. 4, Femur. 5, Ilium. 6, Pleurocentra of sacral vertebrae. 7, Ischium. 8, Pubis. 9, Tarsal ossification. 10, Second, third, and fourth metatarsals. 11, First metatarsal. I, II, III, IV, First, second, third, and fourth digits.

THE SKELETON

441

fibula. The fibular cartilage extends the entire length of the crus, but ossification is confined largely to its proximal end; on the fourteenth day its lower half is represented by a thread-like filament of bone. '

No separate tarsal elements are found in the adult; but in the embryo there are at least three cartilages, viz., a fibulare, tibiale and a large distal element opposite the three main metatarsals. In the course of development, the two proximal elements fuse with one another, and with the distal end of the tibia. The distal element fuses with the three main metatarsals, first with the second, then with the fourth, and lastly with the third (Johnson).

Five digits are formed in the membranous stage of the skeleton. In the case of the fifth chgit, only a small nodule of cartilage (fifth metatarsal) develops and soon disappears. The second, third, and fourth are the chief digits; the first is relatively small. ^Metatarsals 2, 3, and 4 are long and ossify separately in a perichondral fashion. They become applied near their middle and fuse with one another and with the distal tarsal element to form the tarso-metatarsus of the adult (Fig. 250). The first metatarsal is short, lying on the preaxial side of the distal end of the others (Fig. 249); it ossifies after the first phalanx. The number of phalanges is 2, 3, 4, and 5 in the first, second, third, and fourth digits respectively (Fig. 249).

The patella is clearly seen in potash preparations of thirteen-day chicks. At the same time there is a distinct, though iiiiiuite, separate center of ossification in the tarsal region (Fig. 249).

Fig. 250. — Photograph of the skeleton of the foot of a chick embryo of 15 days' incubation. (Preparation and photograph by Roy L. Moodie)

1, 2, 3, 4, First, second, third, and fourth digits. M 2, M 3, M 4, Second, third, and fourth metatarsals.

APPENDIX

GENERAL LITERATURE

V. Baer, C. E., L'eber Entwickelurigsgeschichte der Tiere. Beobachtung

und Reflexion. Konigsbcrg, 1828 u. 1837.

id., 2. Teil — Herausgegeben von Stieda. Konigsberg, 1888. Duval, Mathias, Atlas d'embryologie. (With 40 plates.) Paris, 1889. Foster, M., and Balfour, F. M., The Elements of Embryology. Second

Edition revised. London, 1883. Gadow, Hans, Die Vogel, Bronn's Klassen und Ordniingen des Thier-Reichs,

Bd. VI, Abth. 4, 1898. Handbuch der vergleichenden und experimentellen Entwickelimgslehre der

Wirbeltiere. Edited by Dr. Oskar Hertwig and written by numerous

collaborators. Jena, 1901-1907. Hls, W., LTntersuchungen fiber die erste Anlage des Wirbeltierleibes. Die

erste Entwickelung des Hiihnchens im Ei. Leipzig, 1868. Keibel, F., and Abraham, K., Normaltafeln zur Entwickelungsgeschichte

des Huhnes (Gallus domesticus). Jena, 1900. V. KoLLiKER, A., Entwickelungsgeschichte des Menschen und der hoheren

Thiere. Zweite Aufl. Leipzig, 1879. Marshall, A. M., Vertebrate Embryology. A Text-book for Students and

Practitioners. (Ch. IV, The Development of the Chick.) New York

and London, 1893. MiNOT, C. S., Laboratory Text-book of Embryology. Philadelphia, 1903. Pander, Beitrage zur Entwickelungsgeschichte des Hiihnchens im Ei. Wiirz burg, 1817. Prevost et Dumas, Memoire sur le developpement du poulet dans I'oeuf.

Ann. Sc. Nat., Vol. XII, 1827. Preyer, W., Specielle Physiologic des Embryo. Leipzig, 1885. Remak, R., Untersuchungen iiber die Entwickelung der Wirbelthiere. Berlin, 1855.

LITERATURE — CHAPTER I

Bartelmez, George W., 1912, The Bilaterality of the Pigeon's Egg. A Study in Egg Organization from the First Growth Period of the Oocyte to the Beginning of Cleavage. Journ. of Morph. Vol. 23., pp. 269-328.

CoSTE, M., Histoire generale et particuliere du developpement des corps organises, T. I. (Formation of Egg in Oviduct, see Chap. VI). Paris, 1847-1849.

D 'Hollander, F., Recherches sur I'oogenese et sur la structure et la signification du noyau vitellin de Balbiani chez les oiseaux. Archiv. d'anat. micr., T. VII, 1905.

Gegenbaur, C, Ueber den Bau und die Entwickelung der Wirbeltiereier mit partieller Dottertheilung. Archiv. Anat. u. Phys., 1861.

Glaser, Otto, 1913, On the Origin of Double-yolked Eggs. Biol. Bull.,

Vol. 24, pp. 175-186. HoLL, M., Ueber die Reifung der Eizelle des Huhnes. Sitzungsber. Akad Wiss. Wien, math.-nat. KL, Bd. XCIX, Abth. Ill, 1890.

V. Nathusius, W., Zur Bildung der Eihiillen. Zool. Anz. Bd. XIX, 1896.

Die Entwickelung von Schale und Schalenhaut des Hiihnereies im

Ovidukt. Zeitschr. wiss. Zool., Bd. LV, 1893.

Parker, G. H., Double Hen's Eggs. American Naturalist, Vol. XL. 1906.

Pearl, Raymond and Curtis, M. R, 1912, Studies on the Physiology of

Reproduction in the Domestic Fowl. V. Data Regarding the Physiology

of the Oviduct. Journ. of Exp. Zoology. Vol. 12, pp. 99-132. Riddle, Oscar, 1911, On the Formation, Significance and Chemistry of

the White and Yellow Yolk of Ova. Journ. of Morph., Vol. 22, pp.

455-490. SoNNENBRODT, 1908, Die Wachstunsperiode der Oocyte des Huhns. Arch.

f. mikr. Anat. w. Entw. Bd. 72, pp. 415-480. Waldeyer, W., Die Geschlechtszellen. Handbuch der vergl. und exper.

Entwickelungslehre der \Yirbeltiere. Bd. I, T. 1, 1901.

LITERATURE — CHAPTER II

Andrews, E. A., Some Intercellular Connections in an Egg of a Fowl. The Johns Hopkins University Circular. Notes from the Biological Laboratory, March, 1907.

Barfurth, D., Versuche iiber die parthenogenetische Furchung des Hiihnereies. Arch. Entw.-mech., Bd. 2, 1895.

Blount, Mary, The Early Development of the Pigeon's Egg with Especial Reference to the Supernumerary Sperm-nuclei, the Periblast and the Germ-wall. Biol. Bull., Vol. XIII, 1907.

Duval, M., De la formation du l^lastoderm dans Foeuf d'oiseau. Ann. Sc. Nat. Zool., Ser. 6, T. XVIII, 1884.

Gasser, E., Der Parablast und der Keimwall der Vogelkeimscheibe. Sitzungsber. der Ges. zur Beford. d. ges. Naturwiss. zu Marburg, 1883. Eierstocksei und Eileiterei des Vogels. Ibid, 1884.

Gotte, a., Beitrage zur Entwickelungsgeschichte der Wirbeltiere, II. Die Bildung der Keimblatter und des Blutes im Hiihnerei. Archiv. mikr. Anat., Bd. X, 1874.

Harper, E. H., The Fertilization and Early Development of the Pigeon's Egg. Am. Jour. Anat., Vol. Ill, 1904.

KiONKA, H., Die Furchung des Hiihnereies. Anat. Hefte, Bd. Ill, 1894.

Lau, H., Die parthenogenetische Furchung des Hiihnereies. Inaug. Dissert. Jurjew — Dorpat., 1894.

Oellacher, J., Untersuchungen iiber die Furchung und Blatterl)ildung im Hiihnerei. Studien iiber experimentelle Pathologic von Strieker, Bd

I, 1869. Oellacher, J., Die Veranderungen des unbefruchteten Keimes des Huhnereies im Eileiter und bei Bebriitungsversuchen. Zeitschr. wiss. Zool., Bd. XXII, 1872.

APPENDIX 445

Patterson, J. Thomas, Gastrulation in the Pigeon's Egg; a ^Morphological

and Experimental Study. The Journ. of Morph., Vol. 29, pp. 65-123,

1909. Patterson, J. Thomas, Studies on the Early Dev^elopment of the Hen's

Egg. 1. History of the Early Cleavage and of the Accessory Cleavage.

The Journ. of Morph., Vol. 21, pp. 101-134, 1910. Rauber, a., Ueber die Stellung des Hiihnchens im Entwicklungsplan.

Leipzig, 1876. Sobotta, J., Die Reifung und Befruchtung des Wirbeltiereies. Ergeb.

Anat. u. Entwickelungsgesch., Bd. V, 1895.

LITERATURE — CHAPTER III

Edwards, C. L., The Physiological Zero and the Index of Development for

the Egg of the Domestic Fowl, Gallus Domesticus. Am. Journ. Physiol.,

Vol. VI, 1902. Eycleshymer, a. C, Some Observations and Experiments on the Natural

and Artificial Incubation of the Egg of the Common Fowl. Biol. Bull.,

Vol. XII, 1907. Fere, Cm., Note sur I'influence de la temperature sur I'incubation de I'oeuf

de poule. Journ. de I'anatomie et de la physiologic, Paris, T. XXX,

1894.

LITERATURE — CHAPTERS IV AND V

Assheton, R., An Experimental Examination into the Growth of the Blastoderm of the Chick. Proc. Roy. Soc, London, Vol. LX, 1896.

Balfour, F. M. The Development and Growth of the Layers of the Blastoderm. Quar. Jour. Micr. Sc, Vol. XIII, 1873.

On the Disappearance of the Primitive Groove in the Embryo Chick. lUd.

Balfour, F. M., and Deighton, A Renewed Study of the Germinal Layers of the Chick. Quar. Jour. Micr. Sc, Vol. XXII, 1882.

DissE, J., Die Entwickelung des mittleren Keimblattes im Hiihnerei. Arch, mikr. Anat., Bd. XV, 1878.

DuRSY, Emil, Der Primitivstreif des Hiihnchens. Lahr, 1866.

Duval, Mathias, Etudes sur la hgne primitive de rembr3'on du poulet. Ann. Sc. Nat. Zool., Ser. 6, T. VII, 1S7S.

De la formation du blastoderm dans I'oiuf d'oiseau. Ann. Sc. Nat. Zool., Ser. 6, T. XVIII. Paris, 1884.

Evans, Herbert M. On the Development of the Aorta), Cardinal and UmbiUcal Veins and other Blood-vessels of Vertebrate Embryos from Capillaries. Anatomical Record., Vol. 3, pp. 498-518, 1909.

Fol, H., Recherches sur le developpement des protovertcbres chez I'embryon du poulet. Arch. sc. phys. et nat. Geneve, T. II, 1884.

Gasser, Lieber den Primitivstreifen bei Vogelembryonen. Sitz.-Ber. d. Gcs. z. Beforcl. d. ges. Naturw. z. Marburg, 1877.

Der Primitivestreif bei Vogelembryonen (Huhn w. Gans). Schriften d. Ges. z. Beford. d. ges. Naturw. z. Marburg, Bd. XI, Suppl. Heft 1, 1879.

446 APPENDIX

Gasser, Beitrage zur Kenntnis der Vogelkeimscheibe. Arch. Anat. u

Entw., 1882.

Der Parablast unci der Keimwall der Vogelkeimscheibe. Sitz.-Ber.

d. Ges. z. Beford. d. ges. Naturw. z. Marburg, 1883. GoETTE, A., Beitrage zur Entwickelungsgeschichte der Wirbeltiere. II.

Die Bildung der Keimblatter und des Blutes im Hiihnerei. Arch. mikr.

Anat., Bd. X, 1874. Hertwig, O., Die Lehre von den Keimblattern. Handbuch der vergl. und

exper. Entwickehuigslehre der Wirbeltiere. Vol. I. Jena, 1903. His, W., Der Keimwall des Htihnereies und die Entstehung der para blastischen Zellen. Arch. Anat. und Entw., Bd. I, 1876.

Neue Untersuchung liber die Bildung des Hiihnerembryo. Arch.

Anat. und Entw., 1877.

Lecithoblast und Angioblast der "Wirbelthiere. Histogenetische

Studien. Abh. der math.-phys. Klasse der Konigl. Sachs. Ges. der

Wissenschaften, Bd. XXVI. Leipzig, 1900.

Die Bildung der Somatopleura und der Gefasse beim Hiihnchen.

Anat. Anz., Bd. XXI, 1902. Hubbard, M. E., Some Experiments on the Order of Succession of the

Somites of the Chick. Am. Nat., Vol. 42, pp. 466-471, 1908. Janosik, J., Beitrag zur Kenntnis des Keimwulstes bei Vogeln. Sitz-Ber Akad. Wiss. Wien, math.-phys. KL, Bd. LXXXIV, 1882. Roller, C, Beitrage zur Kenntnis des Hiihnerkeimes im Beginne der Be briitung. Sitzungsber. Wien. Akad. Wiss., math.-nat. KL, 1879. Untersuchungen liber die Blatterbildung im Hlihnerkeim. Arch.

mikr. Anat., Bd. XX, 1881. V. Kolliker, a., Zur Entwickelung der Keimblatter im Hiihnerei. Verb.

phys.-med. Ges. Wlirzburg, Bd. VIII, 1875. KopscH,FR.,Ueber die Bedeutung des Primitivstreifens beim Hiihnerembryo,

und liber die ihm homologen Theile bei den Embryonen der niederen

Wirbeltiere. Intern. Monatschr. f. Anat. u. Phys., Bd. XIX, 1902. MiTROPHANOW, P. J., Teratogene Studien. II. Experimentellen Beo bachtungen liber die erste Anlage der Primitivrinne der Vogel. Arch.

Entw.-mech., Bd. VI, 1898.

Beobachtungen liber die erste Entwickelung der Vogel. Anat.

Hefte, Bd. XII, 1899. Now^\cK, K., Neue Untersuchungen liber die Bildung der beiden primiiren

Keimblatter und die Entstehung des Primitivstreifen beim Hiihnerembryo. Inaug. Diss. Berlin, 1902. Patterson, J. Thos., The Order of Appearance of the Anterior Somites in

the Chick. Biol. Bull., Vol. XIII, 1907. Patterson, J. T. An experimental Study on the Development of the Vascular

Area of the Chick Blastoderm. Biol. Bull. XVI, pp. 83-90, 1909. Peebles, Florence. Some Experiments on the Primitive Streak of the

Chick. Arch. Entw.-mech., Bd. VII, 1898.

A Prehminary Note on the Position of the Primitive Streak and its

Relation to the Embryo of the Chick. Biol. Bull., Vol. IV, 1903.

APPENDIX 447

Peebles, Florence, The Location of the Chick Embryo upon the Blastoderm. Journ. Exp. Zool., Vol. I, 1904. Platt, J. B., Studies on the Primitive Axial Segmentation of the Chick.

Bull. Mus. Comp. Zool. Harv., Vol. 17, 1889. Rabl, C, Theorie des Mesoderms. Morph. Jahrb., Bde. XV und XIX,

1889 and 1892. Rauber, a., Primitivstreifen und Neurula der Wirbelthiere, in normaler

und pathologischer Beziehung. Leipzig, 1877.

Ueber die embryonale Anlage des Hiihnchens. Centralb. d. med.

Wiss., Bd. XII, 1875.

Ueber die erste Entwickelung der Vogel und die Bedeutung der Primi tivrinne. Sitz.-ber. d. naturf. Ges. zu Leipzig, 1876. Rex, Hugo, Ueber das Mesoderm des Vorderkopfes der Ente. Archiv.

■ mikr. Anat., Bd. L., 1897. RiiCKERT, J., Entwickelung der extra-embryonalen Gefasse der Vogel. Hand buch der vergl. w. exp. Entw.-lehre der Wirbelthiere, Bd. I, T. 1,

1906.

Ueber die Abstammung der bluthaltigen Gefassanlagen beim Huhn,

und uber die Entstehung des Randsinus beim Huhn und bei Torpedo.

Sitzungsber. der Bay. Akad. Wiss., 1903. ScHAUiNSLAND, H., Bcitrage zur Biologie und Entwickelung der Hatteria

nebst Bemerkungen uber die Entwickelung der Sauropsiden. Anat.

Anz. XV, 1899. ViALLETOX, Developpement des aortes chez I'embryon de poulet. Journ.

de I'^nat. T. XXVIII, 1892. See also Anat. Anz., Bd. VII, 1892. ViRCHOW, H., Der Dottersack des Huhns. Internat. Beitrage zur wiss.

Med., Bd. I, 1891. Waldeyer, W., Bemerkungen uber die Keimblatter und den Primitivstreifen

bei der Entwickelung des Huhnerembryo. Zeitschr. rationeller Medicin,

1869. Whitman, C. O., A Rare Form of the Blastoderm of the Chick and its Bearing

on the Question of the Formation of the Vertebrate Embryo. Quar.

Journ. Micr. Sc, Vol. XXIII, 1883. WiLLL\MS, Leonard W. The Somites of the Chick. Am. Journ. of Anat.,

Vol. 11, pp. 5.5-100, 1910.

Literature to Chapter VI included in following chapters.

LITERATURE — CHAPTER VII

CHARBONNEiy-SALLE ct Phisalix, De I'evolution postembryonnaire du

sac vitellin chez les oiseaux. C. R. Acad. Sc, Paris, 1886. Dareste, C, Sur I'absence totale de I'amnios dans les embryons de poule.

C. R. Acad. Sc, Paris, T. LXXXVIII, 1879. Duval, M., Etudes histologiques et morphologiques sur les annexes des

embryons d'oiseau. Journ. de I'anat, et de la phys., T. XX, 1884. Etude sur I'origine de Tallantoide chez le poulet. Rev. sc. nat.,

Paris, 1877.

448 APPENDIX

Duval, M., Sur ime organe placentoide chez rembryon des oiseaux. C. R.

Acad. Sc, Paris, 1884. Fromann, C, Ueber die Struktur der Dotterhaut des Huhnes. Sitz.-ber.

Jen. Ges. Medizin u. Naturw., 1879. FuLLEBORN, F., Beitrage zur Entwickelung der Allantois der Vogel. Diss.,

Berlin, 1894. Gasser, E., Beitrage zur Entwickelungsgeschichte der Allantois, der Miiller schen Gange iind des Afters. Frankfurt a. M., 1874. GoTTE, A., Beitrage zur Entwickelungsgeschichte des Darmkanals im Hiihn chen. Tubingen, 1867. HiROTA, S., On the Sero-amniotic Connection and the Foetal Membranes in

the Chick. Journ. Coll. Sc. Imp. Univ. Japan, Vol. VI, Part IV, 1^94. LiLLiE, Frank R., Experimental Studies on the Development of the Organs

in the Embryo of the Fowl (Gallus domesticus): 1. Experiments on the

Amnion and the Production of Anamniote Embryos of the Chick. Biol.

Bull., Vol. V, 1903. 2. The Development of Defective Embryos and

the Power of Regeneration. Biol. Bull., Vol. VII, 1904. Mertens, H., Beitrage zur Kenntniss der Fotushiillen im Vogelei. Meckels

Archiv, 1830. Mitrophanow, p. J., Note sur la structure et la formation de I'enveloppe

du jaune de I'ceuf de la poule. Bibliogr. Anat., Paris, 1898. PopoFF, Demetrius, Die Dottersackgefasse des Huhnes. Wiesbaden, 1894. Pott, R., and Preyer, W., Ueber denGaswechsel und die chemischen Verander ungen des Hiihnereies wahrend der Bebriitung. Archiv. ges. Phys., 1882. Preyer, W., Specielle Physiologic des Embryo. Leipzig, 1885. Ravn, E., Ueber die mesodermfreie Stelle in der Keimscheibe des Huhner embryo. Arch. Anat. u. Entw., 1886.

Ueber den Allantoisstiel des Hiihnerembryo. Verh. Anat. Ges., 1898. ScHAUiNSLAND, H., Die Entwickelung der Eihaute der Reptilien und der

Vogel. Handbuch der vergl. und exp. Entw.-lehre der Wirbeltiere. Bd.

I, T. 2, 1902.

Beitrage zur Entwickelungsgeschichte der Wirbeltiere. II. Beitrage zur

Entwickelungsgeschichte der Eihaute der Sauropsiden. Bibliotheca

Zoologica, 1903. Schenk, S. L., Beitrage zur Lehre vom Amnion. Archiv. mikr. Anat., Bd.

VII, 1871.

Ueber die Aufnahme des Nahrungsdotters wahrend des Embryonal lebens. Sitz.-ber. Akad. Wiss. Wien, math.-nat. Kl., 1897. Shore, T. W., and Pickering, J. W., The Proamnion and Amnion in the

Chick. Journ. of Anat. and Phys., Vol. XXIV, 1889. Soboleff, Die Verletzung des Amnions wahrend der Bebriitung. Mittheil,

embryolog. Inst., Wien, 1883. Strahl, H., Eihaute und Placenta der Sauropsiden. Ergeb. Anat. u. Entw. gesch., Bd. I, 1891. Stuart, T. P. A., A Mode of Demonstrating the Developing Membranes in

the Chick. Journ. Anat. and Phys., London, Vol. XXV, 1899. ViRCHOW, H., Beobachtungen am Hiihnerei; iiber das dritte Keimblatt

im Bereiche des Dottersackes. Virchow's Arch., Bd. LXII, 1874.

APPENDIX 449

ViRCHOW, H., Ueber das Epithel des Dottersackes im Hiihnerei. Diss., Berlin. 1875.

Der Dottersack des Huhnes. Internat. Beitrage zur wissenschaft. Medizin, Bd. I, 1891.

Das Dotterorgan der Wirbeltiere. Zeitschr. wiss. Zool., Bd. LIII, Suppl., 1892.

Das Dotterorgan der Wirbelthiere. Arch. mikr. Anat., Bd. XL, 1892. Dottersyncytium, Keimhautrand und Beziehungen zur Koncrescenzlehre. Ergeb. Anat. u. Entw., Bd. VI, 1897.

Ueber Entwickelungsvorgange, welche sich in den letzten Bruttagen am Hiihnerei abspielen. Anat. Anz., Bd. IV, BerHn, 1889. VuLPiAX, La physiologie de I'amnios et de I'allantoide chez les oiseaux.

Mem. soc. biol., Paris, 1858. Weldox, W. F. R., Prof, de Vries on the Origin of Species. (Includes experiments on amnion.) Biometrica, Vol. I, 1902.

LITERATURE — CHAPTER VIII

Beard, J., Morphological Studies, II. The Development of the Peripheral

Nervous System of Vertebrates. Pt. I. Elasmobranchs and Aves.

Quar. Journ. Micr. Sc, Vol. XXIX, 1888. Beraneck, E., Etudes sur les replis medullaires du poulet. Recueil Zool.

Suisse, Vol. IV, 1887. Bethe, Albrecht, Allgemeine Anatomic und Physiologie des Nervensys tems. Leipzig, 1903. Brandis, F., Untersuchungen iiber das Gehirn der Vogel. Arch. mikr.

Anat., Bd. XLI, 1893; Bd. XLIII, 1894; Bd. XLIV, 1895. Burrows, Montrose T., The Growth of Tissues of the Chick Embryo

Outside the Animal Body, with Special Reference to the Nervous System.

Journ. Exp. Zoology, Vol. 10, pp. 63-83, 1911. Cajal, S. R. y., Sur I'origine et les ramifications des fibres nerveuses de la

moelle embryonnaire. Anat. Anz., Bd. V, 1890.

A quelle epoque aparaissent les expansions des cellules nerveuses de

la moelle epiniere du poulet. Anat. Anz., Bd. V, 1890. Froriep, a., Ueber Anlagen von Sinnesorganen am Facialis, Glossopha ryngeus und Vagus, iiber die genetische Stellung des Vagus zum Hypo glossus, und iiber die Herkunft der Zungenmuskulatur. Arch. Anat.

u. Entw., 1885. Carpenter, Frederick Walton, The Development of the Oculomotor Nerve,

the Ciliary Ganglion, and the Abducent Nerve in the Chick. Bull.

Mus. Comp. Zool. Harv. Vol. XLVIII, 1906. DissE, J., Die erste Entwickelung des Riechnerven. Anat. Hefte, Abth. I,

Bd. IX, 1897. GoLoviNE, E., Sur le developpement du systeme ganglionnaire chez le poulet.

Anat. Anz., Bd. V, 1890. GoRONOwiTscH, N., Die axiale und die laterale (A. Goette) Kopfmetamerie

der Vogeleml^ryonen. Anat. Anz., Bd. VII, 1892.

L'ntersuchungen iiber die Entwickelung der Sogenannten " Ganglien leisten " im Kopfe der Vogelembryonen. Morph. Jahrb., Bd. XX, 1893.

450 APPENDIX

Heinrich, Georg, Untersuchungen iiber die Anlage des Grosshirns beim Hiihnchen. Sitz.-ber. d. Ges. f. Morph. u. Phys. in Munchen, Bd. XII,

1897. Hill, Charles, Developmental History of the Primary Segments of the

Vertebrate Head. Zool. Jahrbucher, Abth. Anat. Bd. XIII, 1900. His, W., Die Neuroblasten und deren Entstehung im embryonalen Mark.

Abh. math.-physik. Klasse, Konigl. Sachs. Ges. Wiss., Bd. XV, 1889. Histogenese und Zusammenhang der Nervenelemente. Arch. Anat. u. Entw., Suppl., 1890. Ueber das frontale Ende des Gehirnrohres. Arch. Anat. u. Entw., 1893. Ueber das frontale Ende und iiber die natiirliche Eintheilung des Gehirnrohres. Verh. anat. Ges., Bd. VII, 1893. His, W. (Jr.)» Ueber die Entwickelung des Bauchsympathicus beim Hiihnchen und Menschen. Arch. Anat. u. Entw., Suppl., 1897. V. KoLLiKER, Ueber die erste Entwickelung der Nervi olfactorii. Sitz.-ber.

phys. med. Ges. zu Wiirzburg, 1890. V. KuPFFER, K., Die Morphogenie des Centralnervensystems. Handbuch der

vergl. und exp. Entwickelungslehre der Wirbeltiere, Kap. VIII, IP, 1905. Lewis, M. R. and Lewis, W. H., The Cultivation of Tissues from Chick

Embroyos in Solutions of NaCl, CaCl2, KCl and NaHCOg. Anatomical

Record, Vol. 5, pp. 277-293. See also Anat. Rec, Vol. 6, nos. 1 and 5, 1911. Marshall, A. M., The Development of the Cranial Nerves in the Chick.

Quar. Journ. Micr. Sc, Vol. XVIII, 1878.

The Segmental Value of the Cranial Nerves. Journ. Anat. and Physiol.,

Vol. XVI, 1882. v. MiHALCOVics, v., Entwickelungsgeschichte des Gehirns. Leipzig, 1877. Onodi, a. D., Ueber die Entwickelung des sympathischen Nervensy stems.

Arch. mikr. Anat., Bd. XXVI, 1886. Rabl, C, Ueber die IMetamerie des Wirbelthierkopfes. Verh. anat. Ges.,

VI, 1892. RuBASCHKiN, W., Ueber die Beziehungen des Nervus trigeminus zur Riech schleimhaut. Anat. Anz., Bd. XXII, 1903. Weber, A., Contribution a Tetude de la metamerism du cerveau anterieur

chez quelques oiseaux. Arch, d'anat. microsc, Paris, T. Ill, 1900. Van Wijhe, J. W., L^eber Somiten und Nerven im Kopfe von Vogel- und

Reptilien-embryonen. Zool. Anz. Bd. IX, 1886.

Ueber die Kopfsegmente und das Geruchsorgan der Wirbelthiere

Zool. Anz., Bd. IX, 1886.

LITERATURE — CHAPTER IX Organs of Special Sense

A. The Eye

Addario, C, Sulla struttura del vitreo embryonale e de' neonati, sulla matrice del vitreo e suU' origine della zonula. Ann. OttalmoL, Anno 30, 1901-1902.

APPENDIX 451

AddariOjC, Ueber die Matrix desGlaskorpers im menschlichen und thierischen

Auge. Vorlauf. Mitth. Anat. Anz., Bd. XXI, 19(32. Agababow, Untersuchiingen iiber die Natur der Zonula ciliaris. Arch.

mikr. Anat., Bd. L, 1897. Angelucci, a., Ueber Entwiekelung und Bau des vorderen Uvealtractus der

Vertebraten. Arch. mikr. Anat., Bd. XIX, 1881. Arnold, J., Beitrage zur Entwickekmgsgeschichte des Auges. Heidelberg,

1874. AssHETON, R., On the Development of the Optic Nerve of Vertebrates, and

the Choroidal Fissure of Embryonic Life. Quar. Journ. Micr. Sc, Vol.

XXXIV, 1892. Bernd, Adolph Hugo, Die Entwiekelung des Pecten im Auge des Hiihn chens aus den Blattern der Augenblase. Bonn, 1905. Cajal, S. R. y., Sur la morphologie et les connexions des elements de la retine

des oiseaux. Anat. Anz. Bd. IV, 1889.

Sur la fine structure du lobe optique des oiseaux et sur I'origine reelle

des nerfs optiques. Int. Monatschr. Anat. u. Phys., Bd. VIII, 1891. Cirincione, G., Ueber die Entwiekelung der Capsula perilenticularis. Arch.

Anat. u. Entw., Suppl. Bd., Jahrg. 1897.

Zur Entwiekelung des Wirbeltierauges. Ueber die Entwiekelung

des Capsula perilenticularis. Leipzig, 1898.

Ueber die Genese des Glaskorpers bei Wirbelthieren. Verh. Anat.

Ges., 17. Versamml. in Heidelberg, 1903. Collin, R., Recherches sur le developpement du muscle sphincter de I'iris

chez les oiseaux. Bibliog. Anat., T. XII, fasc. V. Paris, 1903. Froriep, a., Ueber die Entwiekelung des Sehnerven. Anat. Anz., Bd. VI,

1891.

Die Entwiekelung des Auges der Wirbeltiere. Handb. der vergl. u.

exp. Entw.-l. der Wirbeltiere, Bd. II, 1905. HuscHKE, E., Lieber die erste Entwiekelung des Auges und die damit zusam menhangende Cyklopie. Meckel's Arch., 1832. Kessler, L., Untersuchungen liber die Entwiekelung des Auges, angestellt

am Hiihnchen und Tauben. Dissertation. Dorpat, 1871.

Die Entwiekelung des Auges der Wirbelthiere. Leipzig, 1877. V. Kolliker, a., LTeber die Entwiekelung und Bedeutung des Glaskorpers.

Verh. anat. Ges., 17. Vers. Heidelberg, 1903.

Die Entwiekelung und Bedeutung des Glaskorpers. Zeitschr. wiss.

Zool., Bd. LXXVII, 1904. V. Lenhossek, M., Die Entwiekelung des Glaskorpers. Leipzig, 1903. Lewis, W. H., Wandering Pigmented Cells Arising from the Epithelium of

the Optic Cup, with Observations on the Origin of the M. Sphincter

Pupillffi in the Chick. Am. Journ. Anat., Vol. II, 1903. LocY, W. A., Contribution to the Structure and Development of the Vertebrate Head. Journ. Morph., Vol. XI. Boston, 1895.

Accessory Optic Vesicles in the Chick Embryo. Anat. Anz., Bd. XIV,

1897. NussBAUM, M., Zur Riickbildung embryonaler Anlagen. (Corneal papillae

of chick embryos.) Archiv. mikr. Anat., Bd. LVII, 1901.

452 APPENDIX

NussBAUM, M., Die Pars ciliaris retinae des Vogelauges. Arch. mikr. Anat., Bd.

LVII, 1901.

Die Entwiekelung der Binnenmuskeln des Aiiges der Wirbeltiere.

Arch. mikr. Anat., Bd. LVIII, 1901. Rabl, C, Ziir Frage nach der Entwickehmg des Glaskorpers. Anat. Anz.,

Bd. XXII, 1903.

Ueber den Ban und die Entwickehmg der Linse. II. Reptihen imd

Vogel. Zeitschr. wiss. Zool., Bd. LXV, 1899. Robinson, A., On the Formation and Structure of the Optic Nerve, and its

Relation to the Optic Stalk. Journ. Anat. and Phys. London, 1896. SziLi, A.V. Beitrag zur Kenntniss der Anatomic und Entwickelungsgeschichte

der hinteren Irisschichten, etc. Arch. Opthalm., Bd. LIII, 1902.

Zur Anatomic und Entwickelungsgeschichte der hinteren Irisschichten, etc. Anat. Anz., Bd. XX, 1901.

Zur Glaskorperfrage. Anat. Anz. Bd. XXIV, 1904. ToRNATOLA, Origiuc et nature du corps vitre. Rev. gener. d 'opthalm. Annee

14, 1897. UcKE, A., Epithelreste am Opticus und auf der Retina. Arch. mikr. Anat.,

Bd. XXXVIII, 1891.

Zur Entw^ickelung des Pigmentepithels der Retina. Diss, aus Dorpat.

Petersburg, 1 89 1 . ViRCHOW, H., Facher, Zapfen, Leiste, Polster, Gefasse im Glaskorperraum

von Wirbelthieren, sowie damit in Verbindung stehenden Fragen. Er gebn. Anat. u. Entw., Bd. X. Berlin, 1900. Weysse, a. W., and Burgess, W. S., Histogenesis of the Retina. Am.

Naturalist, Vol. XL, 1906.

B. The Nose

Born, G., Die Nasenhohlen und der Thranennasengang der amnioten Wir belthiere II. Morph. Jahrb., Bd. V, 1879; Bd. VIII, 1883. CoHN, Franz, Zur Entwickelungsgeschichte des Geruchsorgans des Hiihn chens. Arch. mikr. Anat., Bd. LXI, 1903. Dieulafe, Leon, Les fosses nasales des vertebres (morphologic et embry ologie). Journ. de I'anat. et de la phys., T. 40 and 41, 1904 and 1905.

(Translated by Hanau W. Loeb: Ann. of Otol., Rhin. and Laryng., Mar.,

June and Sept., 1900.) Disse, J., Die erste Entwiekelung des Riechnerven. Anat. Hefte, Bd. IX,

1897. Ganin, M., Einige Thatsachen zur Frage iiber das Jacobsohn'sche Organ der

Vogel. Arb. d. naturf. Ges. Charkoff, 1890 (russisch). Abstr. Zool.

Anz., 1890. V. KoLLiKER, A., Ueber die Entwickehmg der Geruchsorgane beim Menschen

und Hiihnchen. Wiirzburger med. Zeitschr., Bd. I, 1860. V. MiHALKOvics, v., Nasenhohle und Jacobson'sche Organ. Anat. Hefte,

I. Abth., Bd. XI, 1898. Peter, Karl, Entwickehmg des Geruchsorgans und Jakobson'sche Organs

in der Reihe der Wirbeltiere. Bildung der ausseren Nase und des

APPENDIX 453

Gaumens. Handbuch der vergl, und experiment. Entwickelimgslehre

der Wirbeltiere. IP, 1902. Preobraschensky, L., Beitrage zur Lehre liber die Entwiekelung des Ge ruchsorganes des Huhnes. Mitth. embryol. Inst. Wien, 1892. PuTELLi, F., Ueber das Verhalten der Zellen der Riechschleimhaut bei

Hiihnerembryonen friiher Stadien. Mitth. embr. Inst. Wien, 1889.

C. The Ear

Hasse, C, Beitrage zur Entwiekelung der Gewebe der hautigen Vogel schnecke. Zeitschr. wiss. Zool., Bd. XVII, 1867. HuscHKE, Ueber die erste Bildungsgeschichte des Auges und Ohres beim

bebriiteten Hiihnchen. Isis von Oken, 1831. Kastschenko, N., Das Schlundspaltengebiet des Hiihnchens. Arch. Anat.

u. Entw., 1887. Keibel, Ueber die erste Bildung des Labyrinthanhanges. Anat. Anz., Bd.

XVI, 1899. Krause, R., Die Entwickekmg des Aquaeductus Vestibuh, s. Ductus endo lymphaticus. Anat. Anz., Bd. XIX, 1901.

Die Entwickekmgsgeschichte des hautigen Bogenganges. Arch. mikr.

Anat., Bd. XXXV, 1890. MoLDENHAUER, W., Die Entwickcking des mittleren und des ausseren Ohres.

Morph. Jahrb., Bd. Ill, 1877. PoLi, C, Sviluppo della vesicula auditiva; studio morphologico. Genoa,

1896.

Zur Entwickekmg der Gehorblase bei den WirbeUieren. Arch. mikr.

Anat., Bd. XLVIII, 1897. Retzius, G., Das Gehororgan der Wirbelthiere. II. Theil, Reptihen Vogel,

Sanger. Stockhokn. 1881-1884. RoTHiG, p., und Brugsch, Theodor, Die Entwickekmg des Labyrintkes

beim Huhn. Archiv. mikr. Anat., Bd. LIX, 1902. RtJDiNGER, Zur Entwickekmg des hautigen Bogenganges des inneren Ohres.

Sitzungsber. Akad. Miinchen, 1888.

LITERATURE — CHAPTER X The Alimentary Tract and Its Appendages

A. The Oral Cavity and Organs

Fraisse, p., Ueber Zahne bei Vogeln. Vortrag, geh. in der phys.-med.

Ges. Wiirzburg, 1880. Gardiner, E. G., Beitrage zur Kenntniss des Epitrichiums und der Bikkmg

des Vogelscknabels. Inaug. Dissert. Leipzig, 1884. Arch. mikr. Anat., Bd. XXIV, 1884. Gauff, E., Anat. L^ntersuchungen iiber die Nervenversorgung der Mund und Nasenhohledrusen der Wirbekiere. Morph. Jahrb., Bd. XIV, 1888. GiACOMiNi, E., Sulle glanduH sakvari degk uccelk. Richerche anatomico embrologiche. Monit. zook Itak, Anno 1, 1890.

454 APPENDIX

GoppERT, E., Die Bedeutimg der Zunge ftir den secundaren Gaumen und den

Ductus naso-pharyngeus. Beobachtungen an Reptilien und Vogeln.

Morph. Jahrb., Bd. XXXI, 1903. Kallius, E., Die mediane Thyreoideaanlage und ihre Beziehung zum Tuber culum impar. Verb. anat. Ges., 17. Vers., 1903.

Beitrage zur Entwickelung der Zunge. Verb. anat. Ges., 15. Vers.

Bonn, 1901. Manno, Andrea, Sopra il niodo onde si perfora e scompare le membrana

faringea negli embrioni di polio. Richerche Lab. Anat. Roma, Vol.

IX, 1902. Oppel, a., Lehrbuch der vergleichenden mikroskopischen Anat. der Wir beltiere. Jena, 1900. Reichel, p., Beitrag zur Morphologie der ^Mundhohlendriisen der Wirbel thiere. Morph. Jahrb., Bd. VIII, 1883. Rose, C., Ueber die Zahnleiste und die Eischwiele der Sauropsiden. Anat.

Anz., Bd. VII, 1892. Sluiter, C. p., Ueber den Eizahn und die Eischwiele einiger Reptilien.

Morph. Jahrb., Bd. XX, 1893. Yarrell, W., On the Small Horny Appendage to the Upper Mandible in

Very Young Chickens. Zool. Journal, 1826.

B. Derivatives of the Emhryonic Pharynx

van Bemmelen, J. F., Die Visceraltaschen und Aortenbogen bei Reptilien

und Vogeln. Zool. Anz., 1886. His, W., Ueber den Sinus praecervicalis und die Thymusanlage. Arch.

Anat. u. Entw., 1886.

Schlundspalten und Thymusanlage. Arch. Anat. u. Entw., 1889. Der Tractus Thyreoglossus und seine Beziehung zum Zungenbein.

Arch. Anat. u. Entw., 1891. Kastschenko, N., Das Schlundspaltengebiet des Hiihnchens. Arch. Anat.

und Entw., 1887. LiESSNER, E., Ein Beitrag zur Kenntniss der Kiemenspalten und ihrer An lagen bei amnioten Wirbelthieren. Morph. Jahrb., Bd. XIII, 1888. Mall, F. P., Entwickelung der Branchialbogen und Spalten des Hiihnchens.

Arch. Anat. und Entw., 1887. DE Meuron, p., Recherches sur le developpement du thymus et de la glande

thyreoide. Dissertation, Geneve, 1886. MiJLLER, W., Ueber die Entwickelung der Schilddriise. Jen. Zeitschr., Bd.

VI, 1871. Seessel, a., Zur Entwickelungsgeschichte des Vorderdarms. Arch. Anat.

und Entw., 1877. Verdun, M. P., Sur les derives branchiaux du poulet. Comptes rendus

Soc. Biol., Tom. V. Paris, 1898.

Derives branchiaux chez les vertebres superieurs. Toulouse, 1898.

APPENDIX 455

C. (Esophagus, Stomach, Intestine

BoRNHAUPT, Th., Uritersuchiingen fiber die Entwickelung des Urogenital systems beim Huhnchen. Inaug. Diss. Riga, 1867. Cattaneo, G., Intorno a un recente lavoro sullo stomaco degli iiccelli. Pavia,

1888.

Istologia e sviluppo del apparato gastrico degli uceelli. Atti della

Soc. Ital. di Sc. Nat., Vol. XXVII, Anno 1884. Milano, 1885. Cazin, M., Recherches anatomiques, histologiques et embryologiques sur

I'appareil gastrique des oiseaux. Ann. Sc. Xat. Zool. 7 ser., Tom. IV,

1888.

Sur le developpement embryonnaire de Testomac des oiseaux. Bull.

de la societe philomathique de Paris. 7 ser., Tom. XI, Paris, 1887. Developpement de la couehe cornee du gesier du poulet et des glandes

qui la seeretent. Comptes rendus, T. CI, 1885. Cloetta, M., Beit rage zur mikroskopischen Anatomic des Vogeldarmes.

Archiv. mikr. Anat., Bd. XLI, 1893. Fleischmaxx, Albert, Morphologische studien uber Kloake und Phallus der

Amnioten. III. Die Vogel, von Dr. Carl Pomayer. Morph. Jahrb.,

Bel. XXX, 1902. Gasser, E., Beitrage zur Entwiekelungsgeschichte der Allantois, Miiller schen Gauge und des Afters. Frankfurt a. M., 1893.

Die Entstehung der Kloakenoffnung bei Hiihnerembryonen. Arch.

Anat. u. Entw., 1880. Maurer, F., Die Entwickelung des Darmsystems. Handb. d. vergl. u.

exp. Entw.-lehre der Wirbeltiere. 11^, 1902. v. MiHALCovics, v., Untersuchungen liber die Entwickelung des Harn- und

Geschlechtsapparates der Amnioten. Internat. Monatschr. Anat. u.

Phys., Bd. II, 1885-1886. MiNOT, C. S., On the Solid Stage of the Large Intestine in the Chick. Journ.

Bos. Soc. Med. Sc, Vol. IV, 1900. Pomayer, Carl. See Fleischmann. Retterer, E., Contributions a I'etude du cloaque et de la bourse de Fabricius

chez des oiseaux. Journ. de I'anat. et de la phys. 21 An. Paris, 1885. Seyfert, Beitrage zur mikroskopischen Anatomic und zur Entwiekelungsgeschichte der blinden Anhange des Darmcanals bei Kaninchen, Taube

unci Sperling. Inaug. Diss. Leipzig, 1887. ScHW^\RZ, D., Untersuchungen des Schwanzendes bei den Embryonen der

Wirbeltiere. Zeitschr. wiss. Zool., Bd. XL VIII, 1889. Stieda, L. LudwiG, L^eber den Bau und die Entwickelung der Bursa Fabricii.

Zeitschr. wiss. Zool., Bd. XXXIV, 1880. Swenander, G., Beitrage zur Kenntniss des Kropfes der Vogel. Zool. Anz.,

Bd. XXIT, 1899. Weber, A., Quelques faits concernant le developpement de Tintestin moyen,

et de ses glandes annexes chez les oiseaux. C. R. Soc. Biol., T. LIV. Paris,

1902. Wenckebach, K. F., De Ontwikkeling en de bouw der Bursa Fabricii. Inaug. Dissert. Leiden, 1888.

456 APPENDIX

D. Liver and Pancreas

Bracket, A., Die Entwickelung unci Histogenese der Leber und des Pancreas.

Ergebnisse d. Anat. u. Entw.-gesch., 1896. Brouha, M., Recherches sur le developpement du foie, du pancreas, de la

cloison mesenterique et des cavites hepato-enteriques chez les oiseaux.

Journ. de Tanat. et phys., T. XXXIV. Paris, 1898.

Sur les premieres phases du foie et sur revolution des pancreas ven traux chez les oiseaux. Anat. Anz., Bd. XIV, 1898. Choronschitzky, B., Die Entstehung der Milz, Leber, Gallenblase, Bauch speicheldriise und des Pfortadersystems bei den verschiedenen Abthei lungen der Wirbelthiere. Anat. Hefte, Bd. XIII, 1900. Felix, W., Zur Leber und Pancreasentwickelung. Arch. Anat. u. Entw., 1892. Frobeen, F., Zur Entwickelung der Vogelleber. Anat. Hefte, 1892. GoTTE, Alex., Beitrage zur Entwickelungsgeschichte des Darmcanals im

Huhnchen. Tubingen, 1867. Hammar, G. a., Ueber Duplicitat ventraler Pancreasanlage. Anat. Anz.,

Bd. XIII, 1897.

Ueber einige Hauptztige der ersten embryonalen Leberentwickelung.

Anat. Anz., Bd. XIII, 1897.

Einige Plattenmodelle zur Beleuchtung der fruheren embryonalen

Leberentwickelung. Arch. Anat. u. Entw., 1893. MiNOT, C. S., On a Hitherto Unrecognized Form of Blood-Circulation without

Capillaries in the Organs of Vertebrata. Proc. Boston Soc. of Nat.

Hist., Vol. XXIX, 1900. ScHREiNER, K. E., Beitrage zur Histologic und Embryologie des Vorder darms der Vogel. Zeitschr. wiss. ZooL, Bd. LXVIII, 1900. Shore, T. W., The Origin of the Liver, Journ. of Anat. and Phys., Vol. XXV,

1890-91. Saint-Remy, Sur le developpement du pancreas chez les oiseaux. Rev.

biol. du Nord de la France. Annee V, 1893.

E. The Respiratory Tract

Bar, M., Beitrage zur Kenntniss der Anatomic und Physiologic der Athemwerkzeuge bei den Vogeln. Zeitschr. wiss. Zool., Bd. LXI, 1896.

Bertelli, D., Sviluppo de sacchi aeriferi del polio. Divisione della cavita celomatica degli uccelli. Atti della Societa Toscana di scienze natural! residente in Pisa. Memorie, Vol. XVII, 1899.

Blumsteix-Judina, Beila, Die Pneumatisation des Markes der Vogelknochen. Anat. Hefte, Abth. I, Bd. XXIX (Heft 87), 1905.

Camp ANA, Recherches d 'anatomic de physiologic, et d 'organogenic pour la determination des lois de la genese et de revolution des especes animals. I. Memoire. Physiologic de la respiration chez les oiseaux. Anatomic de I'appareil pneumatique puhnonnaire, des faux diaphragmes, des seremus et de I'intestin chez le poulet. Paris, Masson, 1875.

Goeppert, E., Die Entwickelung der luftfiihrenden Anhange des Vorderdarms. Handbuch d. vergl. u. exp. Entw.-lehre der Wirbeltiere, Bd. II, T. 1, 1902.

APPENDIX 457

LocY, W. A. and Larsell, O., The Embryology of the Bird's Lung, Based on Observations of the Domestic Fowl. Am. Journ. of Anat., Vol. 19, pp. 447-504, and Vol. 20, pp. 1-44, 1916.

Rathke, M. H., Ueber die Entwickelung der Atemwerkzeuge bei den Vogeln und Saugetieren. Nov. Act. Acad. Caes. Leop. Car., T. XIV. Bonn, 1828.

Selenka, E., Beitrage zur Entwickelungsgeschichte der Luftsiicke des Huhnes. Zeitschr. wiss. Zool., Bd. XVI, 1866.

Strasser, H., Die Luftsacke der Vogel. Morph. Jahrb., Bd. Ill, 1877.

Weber, A., et Buvignier, A., Les premieres phases du developpement du poumon chez les embryons de poulet. Comptes rendus hebd. des seances de la societe de Biologie, Vol. LV. Paris, 1903.

WuNDERLiCH, L., Beitrage zur vergleichenden Anatomie und Entwickelungsgeschichte des unteren Kehlkopfes der Vogel. Nova Acta Acad. Caes. Leop. Carol. Germanicae, Bd. XL VIII, 1884.

LITERATURE — CHAPTER XI

Beddard, F. E., On the Oblique Septa ("Diaphragm" of Owen) in the Passerines and some other Birds. Proc. Zool. Soc. London, 1896.

Bertelli, D., Sullo sviluppo del diaframma dorsale nel Polio. Nota preventiva. Monit. Zool. Ital., Anno IX, 1898.

Contributo alia morfologia ed alio sviluppo del diaframma ornitico. Ibid., 1898.

Bracket, A., Die Entwickelung der grossen Korperhohlen imd ihre Trennung von einander, etc. Ergebnisse d. Anat. u. Entw.-gesch., Bd. VII, 1897.

Broman, Ivar, Die Entwickelungsgeschichte der Bursa omentalis und ahnlicher Recessbildungen bei den Wirbeltieren. Wiesbaden, 1904.

B-ROUHA, M. See Chap. X.

Butler, G. W., On the Subdivision of the Body Cavity in Lizards, Crocodiles and Birds. Proc. Zool. Soc. London, 1889.

Choronschitzky, B. See Chap. X.

Dareste, C, Sur la formation du mesentere et de la gouttiere intestinale dans Tembryon de la poule. Comptes rendus, T. CXII, 1891.

HocHSTETTER, F., Die Entwickelung des Blutgefasssystems. Handbuch der vergl. und exp. Entw.-lehre der Wirbeltiere. IIP, 1903.

Janosik, J., Le pancreas et la rate. Bibliographic Anat. Annee 3. Paris, 1895.

LocKWOOD, C. B., The Early Development of the Pericardium, Diaphragm and Great Veins. Phil. Trans. Roy. Soc, London, Vol. CLXXIX, 1889.

Mall, F. P., Development of the Lesser Peritoneal Cavity in Birds and Mammals. Journ. Morph., Vol. V, 1891.

Maurer, F., Die Entwickehmg des Darmsystems. Handbuch d. vergl. u. exp. Entw.-lehre d. Wirbeltiere, Vol. II, 1906.

Peremeschko, LTeber die Entwickelung der Milz. Sitzungsber. d. Akad. d. Wiss. in Wien, math., naturwiss. Klasse, Bd. LVI, Abth. 2, 1867.

Ravn, E., Die Bildung des Septum transversum beim Hiihnerembryo. Arch. Anat. u. Entw., 1896. See also Anat. Anz., Bd. XV, 1899.

458 APPENDIX

Reichert, Entwickelungsleben im Wirbeltierreich. Berlin, 1840. Remak, Untersuchungen liber die Entwickelung des Wirbeltierreichs, p. 60,

1850-1855. UsKOW, W., Ueber die Entwickelung des Zwerchfells, des Pericardium und

des Coeloms. Arch. mikr. Anat., Bd. XXII, 1883. WoiT, O., Zur Entwickelung der Milz. Anat. Hefte, Bd. IX, 1897.

LITERATURE — CHAPTER XII

V. Baer, K. E., Ueber die Kiemen und Kiemengefasse im den Embryonen

der Wirbeltiere. Meckel's Archiv., 1827. VAN Bemmelen, J., Die Visceraltaschen und Aortenbogen bei Reptilien und

Vogeln. Zool. Anz., 1886. Boas, J. E. V., Ueber die Aortenbogen der Wirbeltiere. Morph. Jahrb.,

Bd. XIII, 1887. Brouha. See Chap. X. HocHSTETTER, F., Die Entw^ickelung des Blutgefasssystems (des Herzens

nebst Herzbeutel und Zwerchfell, der Blut- und Lymphgefasse, der

Lymphdriisen und der Milz in der Reihe der Wirbeltiere). Handbuch

der vergl. und exp. Entwickelungslehre der Wirbeltiere. IIP, 1903. Beitrage zur Entwickelungsgeschichte des Venensystems der Amnioten.

I. Hiihnchen. Morph. Jahrb., Bd. XIII, 1888.

Ueber den Ursprung der Arteria Subclavia der Vogel. Morph. Jahrb,

Bd. XVI, 1890.

Entwickelung des Venensystems der Wirbeltiere. Ergeb. der Anat.

u. Entw., Bd. Ill, 1893. HuscHKE, E., Ueber die Kiemenbogen und Kiemengefasse beim bebriiteten

Hiihnchen. Isis, Bd. XX, 1827. Langer, a., Zur Entwickelungsgeschichte des Bulbus cordis bei Vogeln und

Saugetieren. Morph. Jahrb., Bd. XXII, 1894. LiNDES, G., Ein Beitrag zur Entwickelungsgeschichte des Herzens. Dissertation. Dorpat, 1865. LocY, W. A., The Fifth and Sixth Aortic Arches in Chick Embryos with

Comments on the Condition of the Same Vessels in other Vertebrates.

Anat. Anz., Bd. XXIX, 1906. Mackay, J. Y., The Development of the Branchial Arterial Arches in Birds,

with Special Reference to the Origin of the Subclavians and Carotids.

Phil. Trans. Roy. Soc, London, Vol. CLXXIX, 1889. Masius, J., Quelques notes sur le developpement du coeur chez le poulet.

Arch. Biol., T. IX, 1889. Miller, W. S., The Development of the Postcaval Veins in Birds. Am.

Journ. Anat., Vol. II, 1903. PopoFF, D., Die Dottersackgefasse des Huhnes. Wiesbaden, 1894. Rathke, H., Bemerkungen iiber die Entstehung der bei manchen Vogeln

und den Krokodilen vorkommenden unpaaren gemeinschaftlichen Carotis.

Arch. Anat. u. Phys., 1858. Rose, C, Beitrage zur vergleichenden Anatomie des Herzens der Wirbeltiere. Morph. Jahrb., Bd. XVI, 1890.

APPENDIX 459

Rose, C, Beitrage zur Entwickelungsgeschichte des Herzens. Inaug. Dissert.

Heidelberg, 1888. ToNGE, Morris, On the Development of the Semilunar Valves of the Aorta

and Pulmonary Artery of the Chick. Phil. Trans. Roy. Soc, London,

Vol. CLIX, 1869. Twining, Granville H., The Embryonic History of the Carotid Arteries

in the Chick. Anat. Anz., Bd. XXIX, 1906. ViALLETON, L., Developpement des aortes posterieures chez I'embryon de

poulet. C. R. Soc. Biol., T. III. Paris, 1891.

Developpement des aortes chez Tembryon de poulet. Journ. de

Tanat. et phys., T. XXVIII, 1892. ZucKERKANDL, E., Zur Anat. und Entwickelungsgeschichte der Arterien des

Unterschenkels und des Fusses. Anat. Hefte, Bd. V, 1895.

Zur Anatomie und Entwickelungsgeschichte der Arterien des Vor derarmes. Anat. Hefte, Bd. IV, 1894.

LITERATURE — CHAPTER XIII

Abraham, K., Beitrage zur Entwickelungsgeschichte des Wellensittichs.

Anat. Hefte, Bd. XVII, 1901. Balfour, F. M., On the Origin and History of the Urogenital Organs of

Vertebrates. Journ. of Anat. and Physiol., Vol. X, 1876. Balfour and Sedgwick, On the Existence of a Rudimentary Head Kidney

in the Embryo Chick. Proc. R. Soc, London, Vol. XXVII, 1878. On the Existence of a Head Kidney in the Embryo Chick and on

Certain Points in the Development of the Miillerian Duct. Quar. Journ.

Micr. Sc, Vol. XIX, 1879. BoRNHAUPT, Th., Zur Entwickelung des Urogenitalsystems beim Huhnchen.

Inaug. Diss. Dorpat, 1867. Brandt, A., Ueber den Zusammenhang der Glandula suprarenalis mit dem

parovarium resp. der Epididymis bei Hiihnern. Biolog. Centralbl.,

Bd. IX, 1889.

Anatomisches und allgemeines liber die sog. Hahnenfedrigkeit und

liber anderweitige Geschlechtsanomalien der Vogel. Zeitschr. wiss. Zool.,

Bd. XL VIII, 1889. Felix, W., Zur Entwickelungsgeschichte der Vorniere des Huhnchens Anat. Anz., Bd. V, 1890. Felix und Buhler, Die Entwickelung der Ham- und Geschlechtsorgane.

]. Abschnitt — Die Entwickelung des Harnapparates, von Prof. Felix.

Handbuch der vergl. u. exper. Entw.-lehre der Wirbeltiere, HIS 1904. FiRKET, Jean, Recherches sur I'organogenese des glands sexuelles chez les

oiseaux. Arch, de Biol. Tome 29, pp. 201-351. PI. 5, 1914. FuRBRiNGER, M., Zur vcrgleichendeu Anatomie und Entwickelungsgeschichte

der Excretionsorgane der Vertebraten. Morph. Jahrb., Bd. IV, 1878. Fusari, R., Contribution a I'etude du developpement des capsules surre nales et du sympathetique chez le poulet et chez les mamniiferes. Archives. Hal. de biologic, T. XVI, 1892.

460 APPEXDIX

Gasser, E., Beitrage zur Entwickelungsgeschichte der Allantois, der Muller schen Gange imd des Afters. Frankfurt a. M., 1874.

Die Entstehung des Wolff'schen Ganges beim Huhn. Sitz.-ber.

Naturf. Ges., Marburg, Jahrg. 1875.

Beobachtungen uber die Entstehung des Wolff'schen Ganges bei

Embryonen von Hiihnern und Gansen. Arch. mikr. Anat.. Bd. XIV, 1877. Gasser, E., und Siemmerling, Beitrage zur Entwickekmg des Urogenitalsys tems bei den Huhnerembryonen. Sitz.-ber. Naturf. Ges., Marburg, 1879. Gerhardt, U., Zur Entwickelung der bleibenden Niere. Arch. mikr. Anat.,

Bd. LVII, 1901. HocHSTETTER, F., Zur Morphologie der Vena cava inferior. Anat. Anz., Bd. Ill,

1888. Hoffmann, C. K., Etude sur le developpement de I'appareil urogenital des

oiseaux. Verhandelingen der Koninklyke Akademie van Wetenschap pen. Amsterdam, Tweede Sectie, Vol. I, 1892. Janosik, J., Bemerkungen iiber die Entwickelung der Nebennieren. Archiv.

mikr. Anat., Bd. XXII, 1883.

Histologisch-embryologische Untersuchungen iiber das Urogenital system. Sitzungsber. Akad. Wiss. Wien, math.-nat. Kl., Bd. XCI,

3. Abth., 1885. KosE, W., Ueber die Carotisdriise und das "Chromaffine Gewebe" der Vogel.

Anat. Anz., Bd. XXV, 1904. KowALEvsKY, R., Die Bildung der Urogenitalanlage bei Huhnerembryonen.

Stud. Lab. Warsaw Univ., II, 1875. KuPFFER, C, Untersuchungen iiber die Entwickelung des Harn- und Ge schlechtssystems. Arch. mikr. Anat., Bd. I, 1865; and ibid. Bd. II, 1866. V. MiHALCOVics, v., Untersuchungen iiber die Entwickelung des Harn und Geschlechtsapparates der Amnioten. Intern. Monatschr. Anat.

und Phys., Bd. II, 1885-1886. Miner viNi, R., Des capsules surrenales: Developpement, structure, fonc

tions. Journ. de Tanat. et de la phys, An. XL. Paris, 1904. NussBAUM, M., Zur Differenzierung des Geschlechtes im Thierreich. Arch.

mikr. Anat., Bd. XVIII, 1880.

Zur Entwickelung des Geschlechts beim Huhn. Verh. anat. Ges., Bd

XV, 1901.

Zur Riickbildung embryonaler Anlagen. Arch. mikr. Anat., Bd

LVII, 1901.

Zur Entwickelung des Urogenitalsystems beim Huhn. C. R. Ass.

d. An. Sess., 5. Liege, 1903. Poll, H., Die Entwickelung der Nebennierensysteme. Handbuch der

vergl. und exper. Entwickelungslehre der Wirbeltiere. III^ 1906. Prenant, a., Remarques a propos de la constitution de la glande genitale

indifferente et de I'histogenese du tube seminifere. C. R. Soc. biol.,

Ser. 9, T. II, 1890. Rabl, H., Die Entwickelung und Struktur der Nebennieren bei den Vogeln.

Arch. mikr. Anat., Bd. XXXVIII, 1891. Renson, G., Recherches sur le rein cephalique et le corps de Wolff chez les

oiseaux et les mammiferes. Arch. mikr. Anat., Bd. XXII, 1883.

APPENDIX 461

RucKERT, J., Entwickelung der Excretionsorgane. Ergebnisse der Anat.

u. Entw.-gesch., Bd. I, 1892. ScHREixER, K. E., Ueber die Entwickelung der Amniotenniere. Zeitschr.

wiss. Zool., Bd. LXXI, 1902. Sedgwick, A., Deve opment of the Kidney in its Relation to the Wolffian Body in the Chick. Quart. Journ. IMicr. Sc, Vol. XX, 1880.

On the Early Development of the Anterior Part of the Wolffian Duct and Body in the Chick, together with Some Remarks on the Excretory System of Vertebrata. Quart. Journ. Micr. Sc, Vol. XXI, 1881. Semon, Richard, Die indifferente Anlage der Keimdriisen beim Htihnchen und ihre Differenzierung zum Hoden. Jen. Zeitschr. Naturwiss., Bd. XXI, 1887. SouLiE, E. H., Recherches sur le developpement des capsules surrenales chez les vertebres superieurs. Journ. de I'anat. et phys., Paris, An. XXXIX, 1903. Swift, Charles H., Origin and Early History of the Primordial GermCells in the Chick. American Journal of Anat., Vol. 15, pp. 483516, 1914.

Origin of the Definitive Sex-Cells in the Female Chick and their Relation to the Primordial Germ-Cells. ib. Vol. 18, pp. 441-470, 1915.

Origin of the Sex-Cords and Definitive Spermatogonia in the Male Chick, ib. Vol.20, pp. 375-410, 1916. Waldeyer, W., Eierstock und Ei. Ein Beitrag zur Anatomie und Ent wickelungsgeschichte der Sexualorgane. Leipzig, 1870. Weldon, On the Suprarenal Bodies of Vertebrates. Quar. Journ. Micr. Sc, Vol. XXV, 1884.

LITERATURE — CHAPTER XIV

Agassiz, L., On the Structure of the Foot in the Embryo of Birds. Proc

Boston Soc Nat. Hist., 1848. Bizzozero, G., Neue Untersuchungen iiber den Bau des Knochenmarks der

Vogeln. Arch. mikr. Anat., Bd. XXXV, 1890. See also Arch. Ital. de

Biol., T. XIV, 1891. Blu.mstein-Judixa, Beila, Die Pneumatisation des Markes der Vogelkno chen. Anat. Hefte, Abth. I, Bd. XXIX, 1905. Bracket, A., Etude sur la resorption de cartilage et le developpement des

OS longs chez les oiseaux. Internat. Monatschr. Anat. und Phys., Bd.

X, 1893. Braun, M., Entwickelung des Wellenpapageis. Arb. Zool. Zoot. Inst. Wiirz burg, Bd. V, 1881. Brulle et HuGUENY, Developpement des os des oiseaux. Ann. Sc. Nat.,

Ser. Ill, Zool. T. IV,1845. BuNGE, A., Untersuchungen zur Entwickelungsgeschichte des Beckengiirtels

der Amphibien, Reptilien und Vogel. Inaug. Diss. Dorpat. 1880. CuviER, Extrait d'un memoire sur les progres de I'ossification dans le sternum

des oiseaux. Ann. des Sc Nat., Ser. I, Vol. XXV, 1832. V. Ebner, v., Ueber die Beziehungen der Wirbel zu den LTrwirbel. Sitzungsber.

d. k. Akad. d. Wiss. Wien, math.-naturwiss. Kl., Bd. CI, 3. Abth.. 1892.

462 APPENDIX

Urwirbel und Neugliederiing der Wirbelsaule. Sitzungsber. d. k.

Akad. d. Wiss. Wien, Bd. XCVII, 3. Abth. Wien, 1889, Jahrg., 1888. Froriep, a., Zur Entwickelungsgeschichte der Wirbelsaule, insbesondere

des Atlas und Epistropheus und der Occipitalregion. I. Beobachtungen

an Hiihnerembryonen. Arch. Anat. u. Entw., 1883. Gaupp, E., Die Entwickelung des Kopfskelettes. Handbuch der vergl. u.

exper. Entw.-lehre der Wirbeltiere, Bd. 3, 1905.

Die Entwickelung der Wirbelsaule. Zool. Centralbl., Jahrg. Ill, 1896. Die Metamerie des Schadels. Ergeb. der Anat. u. Entw., 1897. Gegenbaur, C, Untersuchungen zur vergl. Anat. der Wirbelsaule bei

Amphibien und Reptilien. Leipzig, 1864.

Beitrage zur Kenntniss des Beckens der Vogel. Eine vergleichende

anatomische Untersuchung. Jen. Zeitschr. Med. u. Naturw., Bd. VI, 1871. Die Metamerie des Kopfes und die Wirbeltheorie des Kopfskelettes,

im Lichte der neueren Untersuchungen betrachtet und gepriift. Morph.

Jahrb., Bd. XIII, 1888. GoETTE, A., Die Wirbelsaule und ihre Anhange. Arch. mikr. Anat., Bd.

XV, 1878. Hepburn, D., The Development of Diarthrodial Joints in Birds and Mammals. Proc. R. Soc. Edinb., Vol. XVI, 1889. Also in Journ. of Anat.

and Phys., 1889. Jager, G., Das Wirbelkorpergelenk der Vogel. Sitzungsber. Akad. Wien,

Bd. XXXIII, 1858. Johnson, Alice, On the Development of the Pelvic Girdle and Skeleton

of the Hind Limb in the Chick. Quar. Journ. Micr. Sc, Vol. XXIII,

1883. KuLCZYCKi, W., Zur Entwickelungsgeschichte des Schultergiirtels bei den

Vogeln mit besonderer Berucksichtigung des Schliisselbeines (Gallus,

Columba, Anas). Anat. Anz., Bd. XIX, 1901. Leighton, V. L., The Development of the Wing of Sterna Wilsonii. Am.

Nat., Vol. XXVIII, 1894. LuHDER, W., Zur Bildung des Brustbeins und Schultergiirtels der Vogel.

Journ. Ornith., 1871. Mannich, H., Beitrage zur Entwickelung der Wirbelsaule von Eudyptes

chrysocome. Inaug. Diss. Jena, 1902. Mehnert, Ernst, LTntersuchungen liber die Entwickelung des Os Pelvis

der Vogel. Morph. Jahrb., Bd. XIII, 1887.

Kainogenesis als Ausdruck differenter phylogenetischer Energieen.

Morph. Arb., Bd. VII, 1897. Morse, E. S., On the Identity of the Ascending Process of the Astragalus

in Birds w'ith the Intermedium. Anniversary Mem. Boston Soc. Nat.

Hist., 1880. Norsa, E., Alcune richerche sulla morphologia dei membri anteriori degli

uccelli. Richerche fatte nel Laborat Anatomico di Roma e alti labora tori biologici, Vol. IV, fasc. I. Abstract in French in Arch. Ital. biol.,

T. XXII, 1894. Parker, W. K., On the Structure and Development of the Skull of the Common Fowl (Gallus domesticus). Phil. Trans., Vol. CLIX, 1869.

APPEXDIX 463

Parker, W. K., On the Structure and Development of the Birds' Skull.

Trans. Linn. Soc, 1876.

On the Structure and Development of the Wing of the Common Fowl.

Phil. Trans., 1888. Remak, R., Untersuchungen liber die Entwickelung der Wirbeltiere. Berlin,

1850-1855. Rosenberg, A., Ueber die Entwickelung des Extremitiitenskelets bei einigen

durch die Reduction ihrer Gliedmaassen charakteristischen Wirbeltiere.

Zeitschr. wiss. ZooL, Bd. XXIII, 1873. ScHAUiNSLAND, H., Die Entwickelung der Wirbelsaule nebst Rippen und

Brustbein. Handbuch der vergl. und exper. Entw.-lehre der Wirbeltiere, Bd. Ill, T. 2, 1905. Schenk, F., Studien liber die Entwickelung des knochernen Unterkiefers

der Vogel. Sitzungsber. Akad. Wien, XXXIV Jahrg., 1897. Schultze, O., Ueber Eml^ryonale und bleibende Segmentirung. Verh.

Anat. Ges., Bd. X. Berlin, 1896. Stricht, O. van der, Recherches sur les cartilages articulaires des oiseaux.

Arch, de biol., T. X, 1890. SuscHKiN, P., Zur Anatomic und Entwickelungsgeschichte des Schadels der

Raub vogel. Anat. Anz., Bd. XI, 1896.

Zur Morphologic des Vogelskeletts. (1) Schadel von Tinnunculus.

Nouv. Mem. Soc. Imp. des X'atur. de Moscow, T. X\T, 1899. ScHWARCK, W., Beitrage zur Entwickelungsgeschichte der Wirbelsaule bei

den Vogeln. Anat. Studien (Herausgeg. v. Hasse), Bd. I, 1873. WiEDERSHEiM, R., Ucbcr die Entwickelung des Schulter- und Beckenglirtels.

Anat. Anz., Bd. IV, 1889, and V, 1890. WiJHE, J. W. VAN, Ueber Somiten und Nerven im Kopfe von Vogel- und

Reptilienembryonen. Zool. Anz., Jahrg. IX, 1886.

INDEX

Abducens nerve, 267

Abducens nucleus, 262, 263

Abnormal eggs, 2.5

Accessory cleavage of pigeon's egg, 38, 43, 44

Accessory mesenteries, 340, 341

Acustico-facial ganglion complex, 159 160, 262, 268

Air-sacs, 326, 330, 331

Albumen, 18

Albumen-sac, 217, 224

Albuginea of testis, 397

Alecithal ova (see isolecithal)

Allantois, blood-supply of, 222; general, 217; inner wall of, 220; neck of, 143, 144, 316; origin of, 143, 144; outer wall of, 220; rate of growth, 221; structure of inner wall, 223; structure of outer wall, 223

Amnion, effect of rotation of embryo on, 140, 141, 142; functions of, 231; head fold of, 137, 139; later history of, 231; mechanism of formation, 139, 140; muscle fibers of, 231; origin of, 135; secondary folds of, 142

Amnio-cardiac vesicles, 92, 116

AmpuUse of semicircular canals, 291

Anal plate, 143, 182

See also cloacal membrane

Angioblast, 88

Anterior chamber of eye, 278

Anterior commissure of spinal cord, origin of, 244

Anterior intestinal portal, 95 (Fig. 49), 121, 132

Anterior mesenteric artery, 363

Aortic arches, 198, 199, 203, 358362 ; transformations of, 359-361

Appendicular skeleton, 434

Aqueduct of Sylvius, 251.

Archenteron, 55

Area opaca, 39, 50, 61, 86; pellucida, 39, 50, 61; vasculosa, 61, 86; vitellina, 61, 62, 86

Arterial system, 121, 126, 198, 199, 203, 204, 228, 358-363

Atlas, development of, 420

Atrium bursse omentalis, 344

Auditory nerve, 295; ossicles, 299, 432; pit, 168

Auricular canal, 354

Auriculo- ventricular canal, 348; division of, 355

Axis, development of, 420

Axones, origin of, 235

Basilar plate, 429

Beak, 302, 304

Biogenesis, fundamental law of, 4

Blastoderm, 17; diameter of unin cubated, 61; expansion of, 50, 53,

61 Blastopore, 55, 82 Blood-cells, origin of, 118 Blood-islands, origin of, 86, 89 Blood-vessels, origin of, 118 Body-cavity, 115, 205-210, 333 Bony labyrinth, 296 Brain, primary divisions of, 108;

early development of, 147, 156;

later development of, 244-252 Branchial arch, first, skeleton of, 432 Bronchi, 325, 326 Bulbus arteriosus, 198, 201, 202, 348;

fate of, 357 Bursa Fabricii, 314, 317, 319 Bursa omenti ma j oris, 344 Bursa omenti minoris, 344

Canal of Schlemm, 279

Cardinal veins, anterior, 200, 204,

205, 363; posterior, 200, 204, 205,

368 Carina of sternum, 427 Carotid arch, 361 Carotid, common, 362; external 359,

361 ; internal, 359-361 Carpus, 436, 437 Cartilage, absorption of, 408; bones,

definition, 407; calcification of,

409 Caval fold, 344 Cavo-coeliac recess, 344 Cavum sub-pulmonale, 342 Cell-chain hypothesis, 255 Cell theory, \

Central and marginal cells, 41, 42 Central canal of spinal cord, 242

465

466

INDEX

Cerebellum, 155, 251

Cephalic mesoblastic somites, 108, 269, 428

Cerebral flexures, 149, 245

Cerebral ganjilia, 157-162, 262

Cerebral hemispheres, origin of, 151; (see telencephalon)

Cervical flexure, 133, 245

Chalazee, 18

Chemical composition of parts of hen's egg, 20, 21

Chiasma opticus, 154, 249

Choanal, 215, 285

Chondrification, 408

Chorion, 135, 217, 218, 220

Choroid coat of eye. 279; fissure, 166, 281 ; plexus, 248

Chromaffin tissue, 404

Chronology, 64

Cilary processes, 272, 274

Circulation of blood, 121, 122, 197200, 372-376

Circulation of blood, changes at hatching, 376; completion of double, 355

Classification of stages, 64-67

Clavicle, 434, 435

Cleavage of ovum (hen), 39-43

Cleavage of ovum (pigeon), 43-47

Cloaca, 314-319; (see hind-gut)

Cloacal membrane, 315, 318; (see also anal plate)

Coeliac artery, 363

Coelome (see body-cavity)

Coenogenetic aspects of development, 6

Collaterals, origin of, 238

Collecting tubules of mesonephros, 379, 380

CoUiculus palato-pharyngeus, 398

Commissura anterior, 252; inferior, 252 ; posterior, 252 ; trochlearis, 252

Concrescence, theory of, 82, 84

Cones of growth, 235

Conjunctival sac, 279

Coprodseum, 315, 318, 319

Coracoid, 434, 435

Cornea, 278

Corpus striatum, 247

Corpus vitreum, 275

Cortical cords of suprarenal capsules, 405

Cranial flexure, 133, 245; nerves, 261

Cristse acusticse, 295

Crop, 312

Crural veins^ 372

Cushion septum, 355

Cuticle of sheU, 17

Cutis plate, 185, 188

Delimitation of embryo from blastoderm, 91

Dendrites, origin of, 236

Determinants, 7

Diencephalon, early development of, 152; later development of, 249

Dorsal aorta, origin of, 121

Dorsal longitudinal fissure and septum of spinal cord, 243, 244

Dorsal mesentery, 172, 342

Duct of Botallus, 359, 361, 376

Ducts of Cuvier, 200, 204, 207, 361

Ductus arteriosus (see duct of Botalus) ; choledochus (common bileduct), 181, 321; cochlearis, 293; cystico-entericus, 321 ; endolymphaticus, 169, 289; hepato-cysticus, 321; hepato-entericus, 321; venosus (see meatus venosus)

Duodenum, 310, 311

Ear, later development of, 288

Ectamnion, 138

Ectoderm and entoderm, origin of, 52

Ectoderm of oral cavity, limits of, 301

Egg, formation of, 22, 24, 25

Egg-tooth, 302, 303

Embryonic circulation, on the fou.rth day, 372-374; on the sixth day, 374; on the eighth day, 374-376

Embryonic membranes, diagrams of, 219, 220; general, 216; origin of, 135; summary of later historj^, 145

Endocardium, origin of, 119

Endolymphatic duct (see ductus endolymphaticus)

Endolymphatic sac (see saccus endolymphaticus)

Entobronch;, 327, 328

Entoderm, origin of, 52

Ependyma, origin of, 239

Epididymis, 391, 398

Epiphysis, 153, 249

Epiphyses (of long bones), 409

Epistropheus, development of, 420

Epithalamus, 251

Epithelial ceUs of neural tube, 233, 234

Epithelial vestiges of visceral pouches 309

Epoophoion, 401

Equatorial ring of lens, 277-278

Excentricity of cleavage, 41, 47

Excretory system, origin of, 190

External auditory meatus, 297, 300

External form of the embryo, 211

Eye, early development of, 164; later development of, 271

Eyelids, 279-280

INDEX

467

Facial region, development of the,

214, 215, 216 Facialis nerve, 268 Facialis nucleus, 262, 263 Femur, 440 Fertilization, 35 Fibula, 440

First segmentation nucleus, 36 Fissura metotica, 429 Foetal development, 11 Fold of the omentum, 344, 345 Follicles of ovary, 22, 26, 27, 28, 30,

400 Follicular cells, origin of, 27, 400 Foramen, interventricular, 353, 354;

of Monro, 247; of Winslow, 343;

ovale, 355 Foramina, interauricular, 355 Fore-brain, origin of, 108 Fore-gut, 91, 9'3, 172 Formative stuffs, 15 Funiculi prajcervicales, 307

Gall-bladder, 321

Ganglia, cranial and spinal, 156; cranial, 157, 158, 159, 262; spinal, later development of, 254, 257

Ganglion, ciliare, 266; geniculatum, 268; jugulare, 268; olfactorium nervi trigemini, 264; nodosum, 161, 268 ; ~ petrosum, 161, 268; of Remak, 257

Gastric diverticula of body-cavity, 340

Gastrulation, 53, 84

Genetic restriction, law of, 8

Genital ducts, development of, 401

Germ-cells, general characters of, 9-12; comparison of, 12-14

Germ-wall, 47, 48, 69, 90, 128, 129

Germinal cells of neural tube, 233, 234

Germinal disc, 11, 12, 35, 37, 39

Germinal epithelium, 391, 392, 399

Germinal vesicle, 27, 28

Gizzard, 313, 314

Glomeruli of pronephros, 192

Glossopharyngeus, ganglion complex of, 161, 262, 268; nerve, 268; nucleus, 262, 263

Glottis, 332

Gray matter of spinal cord, development of, 240; origin of, 239

Haemal arch of vertebrae, 416, 417

Harderian gland, 280

Hatching, 232

Head, development of, 213

Head-fold, origin of, 91

Head process, 73, 80

Heart, changes of position of, 348, 349; development on second and third days, 200-203; divisions of cavities of, 350 ; ganglia and nerves of, 259; later development of, 348; origin of, 119

Hensen's knot, 73

Hepatic veins, 366

Hepatic portal circulation, 366, 375

Hermaphroditism of embryo, 391

Heterotaxia, 133

Hiatus communis recessum, 343

Hind-brain, origin of, 108

Hind-gut, 143, 172

Hind-limbs, origin of skeleton, 438

Hoffmann's nucleus, 240

Holoblastic ova, 11, 12

Humerus, 436

Hyoid arch, 175: skeleton of, 432

Hyomandibular cleft, 174, 297

Hypoglossus nerve, 269

Hypophysis, 154, 249

Hypothalamus, 251

Ilium, 438, 439

Incubation, normal temperature for, 65, 66

Indifferent stage of sexual organs, 391

Infundibulum (of brain), 154, 249

Infundibulum (of oviduct). See ostium tubae abdominale

Interganglionic commissures, 156

Intermediate cell-mass, 114, 190

Interventricular sulcus, 348, 353

Intervertebral fissure, 412

Intestine, general development of, 310. 311

Iris, 272 : muscles of, 273, 274

Ischiadic veins, 372

Ischium, 438, 439

Isolecithal ova, 11

Isthmus, of brain, 155; of oviduct, 22

Jacobson, organ of, 286 Jugular vein, 363

Kidney, capsule of, 390; permanent, 384-389; secreting tubules of, 390

Lagena, 293

Lamina terminalis, 105, 152, 247, 248

Larva, 11

Laryngotracheal groove, 178, 331,

332 Ijarynx, 332 Latebra, 1 9

Lateral plate of mesoblast, 115 Lateral tongue folds, 305 Lens, 166, 276-278

468

INDEX

Lenticular zone of optic cup, 271

Lesser peritoneal cavity, 344

Ligamentum pectinatuni iridis, 279

Limiting sulci, 130

Lingual glands, 30G

Lip-grooves, 304

Liver, histogenesis of, 323; later development of, 319-323; origin and early development of, 179, 180, 181 ; origin of lobes of, 322 ; primarv ventral ligament of, 335

Lungs,^ 178, 326

Macula utriculi, sacculi, etc., 295

Malpighian corpuscles (mesonephric) origin of, 195

Mammillae of shell, 17

Mandibular aortic arch, 121, 122, 203, 204

Mandibular arch, skeleton of, 431

Mandibular glands, 306

Mantle layer of spinal cord, origin of, 239

Margin of overgrowth, 52, 57

Marginal notch, 60, 84, 85

Marginal velum, 235

Marrow of bone, origin of, 410

Maturation of ovum, 32

Meatus venosus, 199, 364, 366, 368

Medullary cords of suprarenal capsules, 405, 406

Medullary neuroblasts of brain, 262

Medullary plate, 95; position of anterior end of, in neural tube, 102, 103

Megaspheres, 59

Membrana reuniens, 418

Membrane bones, definition of, 407

]\Iembranes of ovum, 10

Membranous labyrinth, 289

Meroblastic ova, 11

Mesencephalon, 108, 155, 251

Mesenchyme, definition of, 116

Mesenteric artery, 363

Mesenteric vein, 366, 367

Mesenteries, 333

Mesentery, dorsal, 172, 342; of the vena cava inferior, 341

Mesoblast, gastral, 110; of the head, origin of, 116, 117; history of between 1 and 12 somites, 109; lateral plate of, 110, 115; of opaque area, origin of, 86, 88; origin of, 74, 78; paraxial, 110; prostomial, 110; somatic layer of, 115; splanchnic layer of, 115

Mesobronchus, 326, 327

Mesocardia lateralia, 200, 207, 334, 337

Mesocardium, origin of, 120

Mesogastrium, 309, 342, 343 Mesonephric arteries, 363 Mesonephric mesentery, 341 Mesonephric tubules, formation of,

195 Mesonephric ureters, 380 Mesonephros, later history of, 378;

origin and early history of, 194 197; see ^^'olffian body Mesothalamus, 251 Mesothelium, definition of, 116 Metacarpus, 436, 437, 438 Metamorphosis, 11 Metanephros, 384-389 Metatarsals, 441 Metathalamus, 251 Metencephalon, 155, 251 Mid-brain (see Mesencephalon) Mid-gut, 172, 181, 310 Mouth, 301 Miillerian ducts, 391; degeneration

in male, 402, 403; origin of, 401,

402, 403 Muscles of iris, 274 Muscle plate, 185, 186 Myelencephalon, 155, 252 Myocardium, origin of, 119 Myotome, 188

Nares, 286

Nephrogenous tissue, 195, 378; of

metanephros, 384, 387 Nephrotome, 114, 190 Neural crest, 156 Neural folds, 97, 99 Neural groove, 97 Neural tube, 95, 105 Neurenteric canal, 73, 82 Neuroblasts, 233-239; classes of, in

spinal cord, 244 Neurocranium, 427, 428 Neuroglia cells, origin of, 239, 240 Neuromeres, 108, 148, 152, 155 Neurone theory, 236, 255, 256 Neuropore, 101, 105 Notochord, later development of,

411 ff; oriirin of, 80; in the region

of the skull, 428

Oblicjue septum, 331, 342 Oculo-motor nerve, 265; nucleus,

262, 263 Odontoid process, origin of, 420 (Esophagus, 179, 310, 312 Olfactory lobe; 247 Olfactory nerve, 263 Olfactory pits, 169, 285 Olfactory A'estibule, 285 Omentum, development of, 343 Omphalocephaly, 120

INDEX

469

Omphalomesenteric arteries, 199,363; veins, 364-366

Ootid, 14

Opaque area, see area opaca

Optic cup, 165, 271 ; lobes, 251 ; nerve, 2S3, 284, 285; stalk, 149, 164, 284, 285; vesicles, accessory, 164

Optic vesicles, primary, 108, 164; secondary, 166

Ora serrata, 272

Oral cavity, 215, 216, 301

Oral glands, 306

Oral plate, 95, 173

Orientation of embryo on yolk, 25, 63

Ossification, 408-411; endochondral, 409; perichondral, 408

Ostium tubse abdominale, 23 ; development of, 402, 403; relation to pronephros, 402

Otocyst, 168; later development of, 289; method of closure, 168

Ovary, 22, 398-401; degeneration of right, 398

Oviducal membranes of ovum, 10

Oviduct, 22; later development of, 403

Ovocyte, 13, 26, 27

Ovogenesis, 12, 26

Ovogonia, 12, 26

Ovum, 2. 10; bilateral symmetry of, 15; follicular membrane of, 10; organization of, 14; polarity of, 14

Palate, 285, 299

Palatine glands, 306

Palingenetic aspects of development,

6 Pancreas, 181, 323-325, 347 Pander's nucleus, 19 Papilla; conjunctivie sclerse, 280 Parabronchi, 328 Parachordals, 428, 429 Paradidvmis, 391, 398 Paraphysis, 248 Parencephalon, 108, 153, 249 Parietal cavity, 92, 116, 207, 208,

333, 334 Paroophoron, 401 Pars copularis (of tongue), 305 Pars inferior iabyrinthi, 289,. 293 Pars superior lal)yrinthi, 2S9, 291 Parthenogenetic cleavage, 35 Patella, 441 Pecten, 281, 282 Pectoral girdle, 434-436 Pellucid area (see area pellucida) Pelvic girdle, 438-440 Periaxial cords, 158, 159, 161 Pericardiaco-peritoneal membrane,

338

Pericardial and pleuroperitoneal cavities, separation of, 333

Pericardium, closure of dorsal opening of, 337; formation of membranous, 338; see parietal cavity.

Periblast, 38, 43, 47; marginal and central 48; nuclei, origin of, 47, 48

Perichondrium, 408

Periderm, 304

Perilymph, 296, 297

Periosteum, 409

Peripheral nervous system, development of, 252

Pfliiger, cords of, 399

Phseochrome tissue, 404

Phalanges, 436, 438; of foot, 441; of wing, 438

Pharynx, derivatives of, 306; early development of, 93-95, 173; postbranchial portion of, 178

Phvlogenetic reduction of skeleton, 411

Physiological zero of development, 65

Physiology of development, 6

Pineal bodv, 153, 249

Placodes, 160, 161

Pleural and peritoneal cavities, separation of, 340

Pleural grooves, 208, 209

Pleuro-pericardial membrane, 338

Pleuroperitoneal membrane, 326; septum, 340, 341

Plica encephali ventralis, 149, 245

Plica mesogastrica, 341, 344, 368

Pneumato-enteric recesses, 209, 340

Pneumatogastric nerve, 268

Polar bodies, 13, 34

Polyspermy, 35, 36, 37

Pons, 252

Pontine flexure, 149, 245

Postanal gut, 182

Postbranchial bodies, 307, 309

Posterior intestinal portal, 132

Postotic neural crest, 160, 161

Precardial plate, 334, 338

Preformation, 6

Pre-oral gut, 174

Pre-oral visceral furrows, 174, 175

Preotic neural crest, 158

Primitive groove, 72

Primitive intestine, 55

Primitive knot, 73

Primitive mouth, 55, 82

Primitive ova, 26, 392, 399

Primitive pit, 73

Primitive plate, 73

Primitive streak, 69; interpretation of, 82; origin of, 74; relation to embryo, 85

Primordia, embryonic, 8

470

INDEX

Primordial cranium, development of,

428 Primordial follicle, 27 Proamnion, 86, 138 Procoracoid, 435 Proctoda^um, 170, 314, 319 Pronephros, 190-193 Pronucleus male and female, 34, 36 Prosencephalon, 108, 149 Proventriculus, 313 Pubis, 438, 439 Pulmo-enteric recesses (see pneu mato-) Pulmonary arteries, 359 Pupil of eye, 166, 272

Radius, 436

Ramus communicans, 254, 257, 259

Recapitulation theory, 3; diagram of, 5

Recessus hepatico-entericus, 343 ; recessus mesenterico-eutericus, 343; recessus opticus, 153; recessus pleuro-peritoneales, 340; recessus pulmo-hepatici, 340; recessus superior sacci omenti, 340

Rectum, 317

Renal corpuscles, 378, 383

Renal portal circulation, 369, 372, 375

Renal veins, 372

Reproduction, development of organs of, 390-403 ^

Respiratory tract, 178, 325

Rete testis, 398

Retina, 274, 275

Retinal zone of optic cup, 271

Rhombencephalon, 108, 155

Ribs, development of, 424, 425

s (abbreviation for somites), 67

Sacrum, 424

Sacculus, 293, 294

Saccus endolymphaticus, 169, 289, 290

Saccus infundibuli, 249

Scapula, 434, 435

Sclerotic coat of eye, 279

Sclerotomes, and vertebral segmentation, 412; components of, 412; occipital, 428; origin of, 185, 186

Seessell's pocket, 174

Segmental arteries, 122, 199, 362

Segmentation cavity, 43, 47, 53 (see also subgerminal cavity)

Semeniferous tubules, 398

Semicircular canals, 291

Semi-lunar valves, 352

Sensory areas of auditory labyrinth, origin of, 296

Septa of heart, completion of, 355,

356, 357 Septal gland of nose, 287 Septum aortico-pulmonale, 351, 352; of auricular canal, 355 ; bulboauricular, 353; cushion, 351, 355; interauricular, 351, 354; interventricular, 351, 353, 354; of sinus venosus, 358

Septum transversum, 208, 209, 334; derivatives of, 339; lateral closing folds of, 334, 337 ; median mass of, 335

Septum trunci et bulbi arteriosi, 351

Sero-amniotic connection, 138, 143, 217

Sexual cords, 393, 394; of ovary, 398; of testis, 395

Sexual differentiation, 394, 395

Sheath cells, 255

Shell, structure of, 17

Shell membrane, 18

Sickle (of Roller), 71

Sinu-auricular aperture, 357, 358

Sinu-auricular valves, 358

Sinus terminalis 86 (see also vena terminalis)

Sinus venosub, 197, 200, 201, 357; horns of, 358; relation to septum transversum, 339

Skeleton, general statement concerning origin, 407

Skull, chondrification of, 429-432; development of, 427; ossification of, 432, 433, 434

Somatopleure, 62, 115

Somite, first, position in embryo. 111

Somites, of the head, 114; mesoblastic, origin of, 110, 111; mesoblastic, metameric value of, 184; primary structure of, 114

Spermatid, 13

Spermatocyte, 13

Spermatogenesis, 12

Spermatogonia, 13

Spermatozoa, period of life Avithin oviduct, 35

Spermatozoon, 9

Spina iliaca, 440

Spinal accessory nerve, 269

Spinal cord, development of, 239

Spinal nerves, components of, 254; development of, 252, 255; bomatic components of, 254; splanchnic components of, 256

Splanchnocranium, 427

Splanchnopleure, 62, 115

Spleen, 345-347

Spongy layer of shell, 17

Stapes, 300

INDEX

471

Sternum, development of, 425-427

Stigma of follicle, 25

Stomach, 179, 313

Stomodaeum, 170, 173

Stroma of gonads, 393 ; of testis, 397

Subcardinal veins, 368, 369

Subclavian artery, 362

Subclavian veins, 363, 364

Subgerminal cavity, 53, 61, 69

Subintestinal vein, 367

Subnotochordal bar, 416, 418

Sulcus lingualis, 298

Sulcus tubo-tympanicus, 298

Supraorbital sinus of olfactory cavity, 285

Suprarenal capsules, 403-406

Sutura cerebralis anterior, 103-105; neurochordalis seu ventralis, 105; terminalis anterior, 105

Sympathetic nervous system, 256261; relation to suprarenals, 406

Sympathetic trunks, primary, 257; secondary, 258

Synencephalon, 108, 153, 249

Syrinx, 332

Tables of development, 68

Tail-fold, 131

Tarsuh, 441

Tectum lobi optici, 251

Teeth, 304

Tela choroidea, 152

Telencephalon and diencephalon,

origin of, 150 Telencephalon, later development of,

245-249; medium, 151, 245 Telolecithal, 11 Ten somite embryo, description of,

122 Testis, 395-398 Tetrads, 33

Thalami optici, 154, 251 Thymus, 308 Thyroid, 178, 307 Tongue, 305 Torus transversus, 248 Trabeculee, of skull, 428, 429; of

ventricles, 353 Trachea, 331, 332 Trigeminal ganglion complex, 160,

267 Trigeminus nerve, 267 ; nucleus (motor), 262, 263 Trochlearis nerve, 266; nucleus, 262,

263 Truncus arteriosus, 198 Tubal fissure, 298, 301 Tubal ridge, 401

Tuberculum impar (of tongue), 305 Tuberculum posterius, 249

Tubo-tympanic cavity, 297-300

Tubules of mesonephros, degeneration of, 380-382; formation of, 195-196; primary, secondary, tertiary, 379, 380

Turbinals, 285, 286, 431

Turning of embryo, 133

Tympanum, 297, 300

Ulna, 436

Umbilical arteries, 363; veins, 367,

368 Umbilicus, 144; of yolk-sac, 216 UnincuVjated blastoderm, structure

of, 69 Ureter, origin of, 384 Urinogenital ridge, 390, 391; system,

later development of, 378, etc. Uroda}um, 314, 319 Uterus, 22 Utriculus, 291, 292 Uvea, 273

Vagina, 22

Vagus, ganglion complex of, 161; nerve, 268; nucleus, 262, 263

Variability, embryonic, 64

Vas deferens, 401

Vasa efferentia, 398

Vascular system, anatomy of, on fourth day, 197-200; origin of, 117

Venous system, 127, 199, 204, 205, 228, 363-372

Velum transversum, 150, 248

Vena cava, anterior, 363, 364; inferior, 368-372

Vena porta sinistra, 367

Vena terminalis, 228; see also sinus terminalis

Ventral aorta, 121

Ventral longitudinal fissure of spinal cord, 243

Ventral mesentery, 131, 182, 343

Vertebrae, articulations of, 421; coalescence of, 424; costal processes of, 418; hypocentrum of, 418; intervertebral ligaments of, 421; ossification of, 421-424; pleurocentrum of, 418; stage of chondrification of, 418; suspensory ligaments of, 421 ;

Vertebral column, 411; condition on fourth day, 414; condition on fifth day, 415, 417; condition on seventh and eighth days, 418, 420; membranous stage of, 414 Vertebral segmentation, origin of,

412 ff Visceral arches, 175; clefts, 174, 307; furrows, 174; pouches, 174;

472

INDEX

/

pouches, early development of, 175178; pouches, fate of, 307, 308

Vitelline membrane, 10, 30, 31

Vitreous humor, 275

ongm

White matter of spinal cord,

of, 239, 241 Wing, origin of skeleton of, 434, 436 Wolffian body (see mesonephros) ; atrophy, 380, 382, 401; sexual and non-sexual portions, 396; at ninetv-six hours, 379; on the sixth^day, 382; on the eighth day, 382, 383 ; on the eleventh day, 385

Wolffian duct, 191, 193, 194, 391, 401

Yolk, 17, 19; formation of, 29 Yolk-sac, 143, 225-231; entoderm

of, 50; blood-vessels of, 227-230;

septa of, 225-227; ultimate fate

of, 230, 231 Yolk-spheres, 19, 20 Yolk-stalk, 132, 225

Zona radiata, 10, 30, 31 Zone of junction, 52, 57 Zones of the blastoderm, 127-129