The Works of Francis Balfour 2-19: Difference between revisions

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in Crustacea.  
in Crustacea.  


1 This is stated to be the case in Moina (Grobben).  
1 This is stated to be the case in Moina (Grobben).
 
 
 
==CHAPTER XX. ECHINODERMATA==
 
THE development of the Echinodermata naturally falls into
two sections:
 
(i) The development of the germinal layers and of the
systems of organs; (2) the development of the larval appendages
and the metamorphosis.
 
The Development of the Germinal Layers and of tJie Systems
 
of Organs.
 
The development of the systems of organs presents no very
important variations within the limits of the group.
 
Holothuroidea. The Holothurians have been most fully
studied (Selenka, No. 563), and may be conveniently taken as
type.
 
The segmentation is nearly regular, though towards its close,
and in some instances still earlier, a difference becomes apparent
between the upper and the lower poles.
 
At the close of segmentation (fig. 247 A) the egg has a
nearly spherical form, and is constituted of a single layer of
columnar cells enclosing a small segmentation cavity. The
lower pole is slightly thickened, and the egg rotates by means of
fine cilia.
 
An invagination now makes its appearance at the lower
pole (fig. 247 B), and simultaneously there become budded off
from tJie cells undergoing the invagination amoeboid cells, which
 
1 The following classification of the Echinodermata is employed in this chapter.
 
I. Holothuroidea. IV. Echinoidea.
 
II. Asteroidea. V. Crinoidea.
 
III. Ophiuroidea.
 
 
 
ECHINODERMATA. 545
 
 
 
eventually form the muscular system and the connective tissue.
These cells very probably have a bilaterally symmetrical origin.
This stage represents the gastrula stage which is common to all
Echinoderms. The invaginated sack is the archenteron. As it
grows larger one side of the embryo becomes flattened, and the
other more convex. On the flattened side a fresh invagination
 
 
 
 
FIG. 247. TWO STAGES IN THE DEVELOPMENT OF HOLOTHURIA TUBULOSA
 
VIEWED IN OPTICAL SECTION. (After Selenka.)
A. Blastosphere stage at the close of segmentation. B. Gastrula stage.
mr. micropyle ; //. chorion; s.c. segmentation cavity; bl. blastoderm; ep. epiblast;
hy. hypoblast; ms. amoeboid cells derived from hypoblast ; a.e. archenteron.
 
arises, the opening of which forms the permanent mouth, the
opening of the first invagination remaining as the permanent
anus (fig. 248 A).
 
These changes give us the means of attaching definite names
to the various parts of the embryo. It deserves to be noted in
the first place that the embryo has assumed a distinctly bilateral
form. There is present a more or less concave surface extending from the mouth to near the anus, which will be spoken
of as the ventral surface. The anus is situated at the posterior
extremity. The convex surface opposite the ventral surface
forms the dorsal surface, which terminates anteriorly in a
rounded prse-oral prominence.
 
It will be noticed in fig. 248 A that in addition to the
primitive anal invagination there is present a vesicle (?/.).
This vesicle is directly formed by a constriction of the primitive
B. II. 35
 
 
 
54 6
 
 
 
HOLOTHUROIDEA.
 
 
 
archenteron (fig. 249 Vpv.), and is called by Selenka the vasoperitoneal vesicle. It gives origin to the epithelioid lining of
the body cavity and water-vascular system of the adult 1 . In the
parts now developed we have the rudiments of all the adult organs.
The mouth and anal involutions (after the separation of the
vaso-peritoneal vesicle) meet and unite, a constriction indicating
their point of junction (fig. 248 B). Eventually the former gives
 
 
 
 
FIG. 248. THREE STAGES IN THE DEVELOPMENT OF HOLOTHURIA TUBULOSA
 
VIEWED FROM THE SIDE IN OPTICAL SECTION. (After Selenka.)
tn. mouth; oe. oesophagus; st. stomach; i. intestine; a. anus; I.e. longitudinal
ciliated band; v.p. vaso-peritoneal vesicle; p.v. peritoneal vesicle; p.r. right peritoneal vesicle ; //. left peritoneal vesicle ; w.v. water- vascular vesicle ; p. dorsal pore
of water- vascular system ; ms. muscle cells.
 
rise to the mouth and cesophagus, and the latter to the remainder of the alimentary canal 2 .
 
The vaso-peritoneal vesicle undergoes a series of remarkable
changes. After its separation from the archenteron it takes
up a position on the left side of this, elongates in an anteroposterior direction, and from about its middle sends a narrow
diverticulum towards the dorsal surface of the body, where an
 
1 The origin of the vaso-peritoneal vesicle is not quite the same in all the species.
In Holothuria tubulosa it is separated from the csecal end of the archenteron; the
remainder of which then grows towards the oral invagination. In Cucumaria the
archenteron forks (fig. 249) ; and one fork forms the vaso-peritoneal vesicle, and the
other the major part of the mesenteron.
 
2 There appears to be some uncertainty as to how much of the larval cesophagus is
derived from the stomodaeal invagination.
 
 
 
ECHINODERMATA.
 
 
 
547
 
 
 
opening to the exterior becomes formed (fig. 248 B, /.). The
diverticulum becomes the madreporic canal, and the opening
the dorsal pore.
 
The vaso-peritoneal vesicle next divides into two, an anterior vesicle (fig. 248 B, w.v.), from which is derived the
epithelium of the water-vascular system, and a posterior (fig.
248 B, /.?;.), which gives rise to the epithelioid lining of the body
cavity. The anterior vesicle (fig. 248 C, w.v.) becomes fivelobed, takes a horseshoe-shaped form, and grows round the
oesophagus (fig. 256, w.v.r). The five lobes form the rudiments
of the water-vascular prolongations into the tentacles. The
remaining parts of the water-vascular system are also developed
as outgrowths of the original vesicle. Five of these, alternating
with the original diverticula, form the five ambulacral canals,
from which diverticula are produced into the ambulacral feet ; a
sixth gives rise to the Polian vesicle. The remaining parts of
the original vesicle form the water-vascular ring.
 
We must suppose that eventually the madreporic canal loses
its connection with the exterior so as to hang loosely in the
interior, though the steps of this process do not appear to
have been made out.
 
The original hinder peritoneal vesicle grows rapidly,
and divides into two (fig. 248 C,
pi. and pr.}, which encircle the
two sides of the alimentary
canal, and meet above and
below it. The outer wall of
each of them attaches itself to
the skin, and the inner one to
the alimentary canal and watervascular system ; in both cases
the walls remain separated
from the adjacent parts by a
layer of the amoeboid cells
already spoken of. The cavity
of the peritoneal vesicles becomes the permanent body
cavity. Where the walls of
 
 
 
 
-ME
 
 
 
FIG. 249. LONGITUDINAL SECTION
 
THROUGH AN EMBRYO OF CUCUMARIA
DOLIOLUM AT THE END OF THE FOURTH
DAY.
 
Vpv. vaso-peritoneal vesicle; ME.
mesenteron; Blp., Ptd. blastopore, proctodaeum.
 
352
 
 
 
548 HOLOTHUROIDEA.
 
 
 
the two vesicles meet on the dorsal side, a mesentery, suspending the alimentary canal and dividing the body cavity longitudinally, is often formed. In other parts the partition walls
between the two sacks appear to be absorbed.
 
The amoeboid cells, which were derived from the invaginated
cells, arrange themselves as a layer round all the organs (fig.
249). Some of them remain amoeboid, attach themselves to the
skin, and form part of the cutis; and in these cells the calcareous spicula of the larva and adult are formed. Others
form the musculature of the larval alimentary tract, while the
remainder give rise to the musculature and connective tissue of
the adult.
 
The development of the vascular system is not known, but the discovery
of Kowalevsky, confirmed by Selenka, that from the walls of the watervascular system corpuscles are developed, identical with those in the bloodvessels, indicates that it probably develops in connection with the watervascular system. The observations of Hoffmann and Perrier on the communication of the two systems in the Echinoidea point to the same conclusion.
Though nothing very definite is known with reference to the development of
the nervous system, Metschnikoff suggests that it develops in connection
with the thickened bands of epiblast which are formed by a metamorphosis
of the ciliated bands of the embryo, and accompany the five radial tubes
(vide p. 555). In any case its condition in the adult leaves no doubt of its
being a derivative of the epiblast.
 
From the above description the following general conclusions
may be drawn :
 
(1) The blastosphere stage is followed by a gastrula stage.
 
(2) The gastrula opening forms the permanent anus, and the
mouth is formed by a fresh invagination.
 
(3) The mesoblast arises entirely from the invaginated cells,
but in two ways :
 
(a) As scattered amoeboid cells, which give origin to the
muscles and connective tissue (including the cutis) of the body
wall and alimentary tract.
 
(&) As a portion separated off from the archenteron,
which gives rise both to the epithelioid lining of the body cavity,
and of the water-vascular system.
 
(4) The oesophagus is derived from an invagination of the
epiblast, and the remainder of the alimentary canal from the
archenteron.
 
 
 
ECHINODERMATA. 549
 
 
 
(5) The embryonic systems of organs pass directly into those
of the adult.
 
The development of Synapta diverges, as might be expected, to a very
small extent from that of Holothuria.
 
Asteroidea. In Asterias the early stages of development conform to
our type. There arise, however, two bilaterally symmetrical vaso-peritoneal
diverticula from the archenteron. These diverticula give rise both to the
lining of the body cavity and water-vascular system. With reference to
the exact changes they undergo there is, however, some difference of opinion.
Agassiz (543) maintains that both vesicles are concerned in the formation of
the water-vascular system, while Metschnikoff (560) holds that the watervascular system is entirely derived from the anterior part of the larger left
vesicle, while the right and remainder of the left vesicle form the body
cavity. MetschnikofFs statements appear to be the most probable. The
anterior part of the left vesicle, after separating from the posterior, grows
into a five-lobed rosette (fig. 260, /), and a madreporic canal (h] with a dorsal
pore opening to the exterior. The rosette appears not to grow round the
oesophagus, as in the cases hitherto described. But the latter is stated to
disappear, and a new oesophagus to be formed, which pierces the rosette,
and places the old mouth in communication with the stomach. Except
where the anus is absent in the adult, the larval anus probably persists.
 
Ophiuroidea. The early development of the Ophiuroidea is not so
fully known as that of other types. Most species have a free-swimming
larva, but some (Amphiura) are viviparous.
 
The early stages of the free-swimming larvae have not been described,
but I have myself observed in the case of Ophiothrix fragilis that the
segmentation is uniform, and is followed by the normal invagination. The
opening of this no doubt remains as the larval anus, and there are probably
two outgrowths from this to form the vaso-peritoneal vesicles. Each of these
divides into two parts, an anterior lying close to the oesophagus, and a
posterior close to the stomach. The anterior on the right side aborts ; that
on the left side becomes the water-vascular vesicle, early opens to the
exterior, and eventually grows round the oesophagus, which, as in Holothurians, becomes the oesophagus of the adult. The posterior vesicles give rise
to the lining of the body cavity, but are stated by Metschnikoff to be at first
solid, and only subsequently to acquire a cavity the permanent body cavity.
The anus naturally disappears, since it is absent in the adult. In the
viviparous type the first stages are imperfectly known, but it appears that
the blastopore vanishes before the appearance of the mouth. The development of the ^vaso-peritoneal bodies takes place as in the free-swimming
larvae.
 
Echinoidea. In the Echinoidea (Agassiz, No. 542, Selenka, No. 564)
there is a regular segmentation and the normal invagination (fig. 250 A).
The amoeboid mesoblast cells arise as two laterally placed masses, and give
rise to the usual parts. The archenteron grows forward and bends towards
 
 
 
550
 
 
 
CRINOIDEA.
 
 
 
the ventral side (fig. 250 B). It becomes (fig. 250 C) divided into three
chambers, of which the two hindermost (d and c) form the stomach and
intestine ; while the anterior forms the oesophagus, and gives rise to the
 
 
 
 
FIG. 250. THREE SIDE VIEWS OF EARLY STAGES IN THE DEVELOPMENT OF
 
STRONGYLOCENTRUS. (From Agassiz.)
 
a, anus (blastopore) ; d. stomach ; o. oesophagus ; c . rectum ; w. vaso-peritoneal
vesicle ; v. ciliated ridge ; r. calcareous rod.
 
vaso-peritoneal vesicles. These latter appear as a pair of outgrowths
(fig. 251), but become constricted off as a single two-horned vesicle, which
subsequently divides into two. The left of these
is eventually divided, as in Asteroids, into a
peritoneal and water-vascular sack, while the
right forms the right peritoneal sack. An oral
invagination on the flattened ventral side meets
the mesenteron after its separation from the
vaso-peritoneal vesicle. The larval anus persists, as also does the larval mouth, but owing
to the manner in which the water-vascular
rosette is established the larval oesophagus appears to be absorbed, and to be replaced by a
fresh oesophagus.
 
Crinoidea. Antedon, the only Crinoid
so far studied (Gotte, No. 549), presents some
not inconsiderable variations from the usual
Echinoderm type. The blastopore is placed on
the somewhat flattened side of the oval blastosphere, and not, as is usual, at the hinder end.
 
The blastopore completely closes, and is not converted into the permanent anus. The archenteron gives rise to the epithelioid lining of both body
cavity and water-vascular system. These parts do not, however, appear as
a single or paired outgrowth from the archenteron, but as three distinct
outgrowths which are not formed contemporaneously. Two of them are first
 
 
 
 
FIG. -251. DORSO-VENTRAL VIEW OF AN EARLY
LARVA OF STRONGYLOCENTRUS. (From Agassiz.)
 
a. anus ; d. stomach ; o.
oesophagus ; w. vaso-peritoneal vesicle; r. calcareous
rod.
 
 
 
ECHINODERMATA.
 
 
 
551
 
 
 
formed and become the future body cavity; but their lumens remain distinct.
Jngmally appearing as lateral outgrowths, the right one assumes a dorsal
position and sends a prolongation into the stalk (fig. 252 rp'\ and
the left one assumes first a ventral, and then an oral position (fur
252 lp\
 
The third outgrowth of the archenteron gives rise to the water-vascular
vesicle. It first grows round the region of the future oesophagus and so
forms the water-vascular ring.
The wall of the ring then
grows towards the body wall
so as to divide the oral (left)
peritoneal vesicle into two
distinct vesicles, an anterior
and a posterior, shewn in fig.
253, lp' and lp. Before this
division is completed, the
water-vascular ring is produced in front into five pro
 
 
 
FIG. 252. LONGITUDINAL SECTION THROUGH
AN ANTEDON LARVA. (From Carpenter: after
Gotte.)
 
 
 
al. mesenteron ; -wv. water- vascular ring ;
lp. left (oral) peritoneal vesicle; rp. right peritoneal vesicle ; rp'. continuation of right vesicle
into the stalk ; st. stalk.
 
 
 
cessesthe future tentacles
(fig. 252, wv) which project
into the cavity of the oral
vesicle (lp\ After the oral
peritoneal space has become
completely divided into two parts, the anterior dilates (fig. 253, //) greatly,
and forms a large vestibule at the anterior end of the body. This vestibule
(lp'} next acquires a communication with the mesenteron, shewn in fig. 253
at m. The anterior wall of this vestibule is finally broken through. By this
rupture the mesenteron is placed in communication with the exterior by the
opening at m, while at the same time the tentacles of the water-vascular ring
(/) project freely to the exterior. Such is Gotte's account of the prge-oral
body space, but, as he himself points out, it involves our believing that the
lining of the diverticulum derived from the primitive alimentary vesicle
becomes part of the external skin. This occurrence is so remarkable, that
more evidence appears to me requisite before accepting it.
 
The formation of the anus occurs late. Its position appears to be the
same as that of the blastopore, and is indicated by a papilla of the mesenteron attaching itself to the skin on the ventral side (fig. 253, an). It eventually becomes placed in an interradial space within the oral disc of the adult.
The water-vascular ring has no direct communication with the exterior, but
the place of the madreporic canal of other types appears to be taken in
the larva by a single tube leading from the exterior into the body cavity, the
external opening of which is placed on one of the oral plates (vide p. 571) in
the next interradial space to the right of the anus, and a corresponding
diverticulum of the water-vascular ring opening into the body cavity. The
line of junction between the left and right peritoneal vesicles forms in the
larva a ring-like mesentery dividing the oral from the aboral part of the body
 
 
 
552
 
 
 
CRINOIDEA.
 
 
 
cavity. In the adult 1 the oral section of the larval body cavity becomes the
ventral part of the circumvisceral division of the body cavity, and the
subtentacular canals of the arms and disc ; while the aboral section becomes
the dorsal part of the circumvisceral division of the body cavity, the cceliac
canals of the arms, and the cavity of the centro-dorsal piece. The primitive
 
 
 
,+wr
 
 
 
 
FIG. 253. LONGITUDINAL SECTION THROUGH THE CALYX OF AN ADVANCED
PENTRACRINOID ANTEDON LARVA WITH CLOSED VESTIBULE.
 
(From Carpenter ; after Gotte.)
 
ae. epithelium of oral vestibule; ;//. mouth; al. mesenteron; an. rudiment of
permanent anus; lp. posterior part of left (oral) peritoneal sack; lp' '. anterior part of
left (oral) peritoneal sack; wr. water-vascular ring; /. tentacle; mt. mesentery;
rp. right peritoneal sack; rp '. continuation of right peritoneal sack into the stalk;
r. roof of tentacular vestibule.
 
distinction between the sections of the larval body cavity becomes to a large
extent obliterated, while the axial and intervisceral sections of the bodycavity of the adult are late developments.
 
The more important points in the development indicated in
the preceding pages are as follows :
 
(i) The blastosphere is usually elongated in the direction
of the axis of invagination, but in Comatula it is elongated
transversely to this axis.
 
1 Vide P. H. Carpenter, "On the genus Actinometra." Linnean Trans., and
Series, Zoology, Vol. n., Part I., 1879.
 
 
 
ECHINODERMATA. 553
 
 
 
(2) The blastopore usually becomes the permanent anus,
but it closes at the end of larval life (there being no anus in the
adult) in Ophiuroids and some Asteroids, while in Comatula it
closes very early, and a fresh anus is formed at the point where
the blastopore was placed.
 
(3) The larval mouth always becomes the mouth of the
adult.
 
(4) The archenteron always gives rise to outgrowths which
form the peritoneal membrane and water-vascular systems. In
Comatula there are three such outgrowths, two paired, which
form the peritoneal vesicles, and one unpaired, which forms the
water-vascular vesicle. In Asteroids and Ophiuroids there are
two outgrowths. In Ophiuroids both of these are divided into a
peritoneal and a water-vascular vesicle, but the right watervascular vesicle atrophies. In Asteroids only one water-vascular
vesicle is formed, which is derived from the left peritoneal vesicle.
In Echinoids and Holothuroids there is a single vaso-peritoneal
vesicle.
 
(5) The water- vascular vesicle grows round the larval
oesophagus in Holothuroids, Ophiuroids, and Comatula ; in
these cases the larval oesophagus is carried on into the adult.
In other forms the water-vascular vesicle forms a ring which
does not enclose the cesophagus (Asteroids and Echinoids);
in such cases a new oesophagus is formed, which perforates this
ring.
 
Development of the larval appendages and metamorphosis.
 
Holothuroidea. The young larva of Synapta, to which J.
Muller gave the name Auricularia (fig. 255), is in many respects
the simplest form of Echinoderm larva. With a few exceptions
the Auricularia type of larva is common to the Holothuria.
 
It is (fig. 254 A and fig. 255) bilaterally symmetrical, presenting a flattened ventral surface, and a convex dorsal one.
The anus (an) is situated nearly at the hinder pole, and the
mouth (m) about the middle of the ventral surface. In front
of the mouth is a considerable process, the prae-oral lobe.
Between the mouth and anus is a space, more or less concave
according to the age of the embryo, interrupted by a ciliated
 
 
 
554
 
 
 
AURICULARIA.
 
 
 
A similar ciliated ridge is
A E
 
 
 
ridge a little in front of the anus,
present on the ventral surface
of the prae-oral lobe immediately in front of the mouth.
The anal and oral ridges are
connected by two lateral ciliated bands, the whole forming
a continuous band, which,
since the mouth lies in the
centre of it (fig. 255), may be
regarded as a ring completely
surrounding the body behind
the mouth, or more naturally
as a longitudinal ring.
 
The bilateral Auricularia
is developed from a slightly
elongated gastrula with an uniform covering of cilia. The
gastrula becomes flattened on the oral side. At the same time
the cilia become specially developed on the oral and anal ridges,
and then on the remainder of the ciliated ring, while they are
 
 
 
 
FIG. 254. A. THE LARVA OF A HOLOTHUROID. B. THE LARVA OF AN ASTEROID.
 
;//. mouth; st. stomach; a. anus; l.c>
primitive longitudinal ciliated band; pr.c.
prae-oral ciliated band.
 
 
 
 
FIG. 155. DIAGRAMMATIC FIGURES REPRESENTING THE EVOLUTION OF AN
AURICULARIA FROM THE SIMPLEST ECHINODERM LARVAL FORM. (Copied from
MUller.)
 
The black line represents the ciliated ridge. The shaded part is the oral side of
the ring, the clear part the aboral side.
 
/;;. mouth; an. anus.
 
simultaneously obliterated elsewhere ; and so a complete Auricularia is developed. The water-vascular ring in the fully-developed
larva has already considerably advanced in the growth round the
oesophagus (fig. 256 w.v.r).
 
Most Holothurian larvae, in their transformation from the
bilateral Auricularia form to the radial form of the adult, pass
through a stage in which the cilia form a number of transverse
 
 
 
ECHINODERMATA.
 
 
 
555
 
 
 
 
-2>.v
 
 
 
rings, usually five in number, surrounding the body. The
stages in this metamorphosis are shewn in figs. 256, 257, and
258.
 
The primitive ciliated band,
at a certain stage of the metamorphosis, breaks up into a
number of separate portions
(fig. 256), the whole of which are
placed on the ventral surface.
Four of these (fig. 257 A and B)
arrange themselves in the form
of an angular ring round the
mouth, which at this period projects considerably. The remaining portions of the primitive
band change their direction from
a longitudinal one to a transverse (fig. 257 B), and eventually
grow into complete rings (fig.
2570). Of these there are five.
The middle one (257 B) is the
first to develop, and is formed
from the dorsal parts of the
primitive ring. The two hinder
rings develop next, and last of
all the two anterior ones, one of
which appears to be in front of the mouth (fig. 257 C).
 
The later development of the mouth, and of the ciliated ridge
surrounding it, is involved in some obscurity. It appears from
Metschnikoff (No. 560) that an invagination of the oesophagus
takes place, carrying with it the ciliated ridge around the mouth.
This ridge becomes eventually converted into the covering for
the five tentacular outgrowths of the water- vascular ring (fig.
258), and possibly also forms the nervous system.
 
The opening of the cesophageal invagination is at first behind
the foremost ciliated ring, but eventually comes to lie in front of
it, and assumes a nearly terminal though slightly ventral position
(fig. 258). No account has been given of the process by which
this takes place, but the mouth is stated by Metschnikoff (though
 
 
 
FIG. 256. FULL-GROWN LARVA OF
SYNAPTA. (After Metschnikoff.)
 
m. mouth ; st. stomach ; a. anus ;
p.v. left division of perivisceral cavity,
which is still connected with the watervascular system ; w.v.r. water-vascular
ring which has not yet completely encircled the oesophagus; I.e. longitudinal
part of ciliated band ; pr.c. prae-oral part
of ciliated band.
 
 
 
556
 
 
 
BIPINNARIA.
 
 
 
Miiller differs from him on this point) to remain open throughout. The further changes in the metamorphosis are not considerable. The ciliated bands disappear, and a calcareous ring
of ten pieces, five ambulacral and five interambulacral, is formed
round the oesophagus. A provisional calcareous skeleton is also
developed.
 
All the embryonic systems of organs pass in this case
directly into those of the adult.
 
The metamorphosis of most Holothuroidea is similar to that just
described. In Cucumaria (Selenka) there is however no Auricularia stage,
and the uniformly ciliated stage is succeeded by one with five transverse
 
 
 
 
FIG. 257. THREE STAGES IN THE DEVELOPMENT OF SYNAPTA. A and B
are viewed from the ventral surface, and C from the side. (After Metschnikoff.)
 
m. mouth; oe. oesophagus; pv. walls of the perivisceral cavity; wv. longitudinal
vessel of the water- vascular system; p. dorsal pore of water-vascular system;
cr. ciliated ring formed round the mouth from parts of the primitive ciliated
band.
 
bands of cilia, and a prae-oral and an anal ciliated cap. The mouth is at
first situated ventrally behind the prse-oral cap of cilia, but the prae-oral
cap becomes gradually absorbed, and the mouth assumes a terminal
position.
 
In Psolinus (Kowalevsky) there is no embryonic ciliated stage, and the
adult condition is attained without even a metamorphosis. There appear to
 
 
 
ECHINODERMATA.
 
 
 
557
 
 
 
 
be five plates surrounding the
mouth, which are developed before
any other part of the skeleton, and
are regarded by P. H. Carpenter
(No. 548) as equivalent to the five
oral plates of the Crinoidea. The
larval condition with ciliated bands
is often spoken of as the pupa stage,
and during it the larvae of Holothurians proper use their embryonic
tube feet to creep about.
 
Asteroidea. The commonest and most thoroughly
investigated form of Asteroid
larva is a free swimming form
known as Bipinnaria.
 
This form in passing from
the spherical to the bilateral
condition passes through at
first almost identical changes
to the Auricularian larva.
The cilia become at an early
period confined to an oral
and anal ridge.
 
The anal ridge gradually extends dorsalwards, and finally
forms a complete longitudinal post-oral ring (fig. 259 A) ; the
oral ridge also extends dorsalwards, and forms a closed prae-oral
ring (fig. 259 A), the space within which is left unshaded in my
figure.
 
The presence of two rings instead of one distinguishes the
Bipinnaria from the Auricularia. The two larvae are shewn side
by side in fig. 254, and it is obvious that the two bands of the
Bipinnaria are (as pointed out by Gegenbaur) equivalent to the
single band of the Auricularia divided into two. Ontologically,
however, the two bands of Bipinnaria do not appear to arise
from the division of a single band.
 
As the Bipinnaria grows older, a series of arms grows out
along lines of the two ciliated bands (fig. 259 C), and, in many
cases, three special arms are formed, not connected with the
ciliated bands, and covered with warts. These latter arms are
 
 
 
FlG. 258. A LATE STAGE IN THE DEVELOPMENT OF SYNAPTA. (After Metschnikoff.)
 
The figure shews the vestibular cavity
with retracted tentacles ; the ciliated bands ;
the water-vascular system, etc.
 
p. dorsal pore of water-vascular system ;
pv. walls of perivisceral cavity; ms. amoeboid cells.
 
 
 
558
 
 
 
BIPINNARIA.
 
 
 
known as brachiolar arms, and the larvae provided with them
as Brachiolaria (fig. 259 D).
 
As a rule the following arms can be distinguished (fig. 259 C and D), on
the hinder ring (Agassiz' nomenclature) a median anal pair, a dorsal anal
pair, and a ventral anal pair, a dorsal oral pair, and an unpaired anterior
dorsal arm ; on the prae-oral ring a ventral oral pair, and sometimes (Miiller)
an unpaired anterior ventral arm.
 
The three brachiolar arms arise as processes from the base of the
unpaired dorsal arm, and the two ventral oral arms. The extent of the
development of the arms varies with the species.
 
 
 
 
 
FIG. 259. DIAGRAMMATIC REPRESENTATION OF VARIOUS FORMS OF ASTEROID
LARWE. A, B, C, BIPINNARIA; D, BRACHIOLARIA. (Copied from Muller.)
The black lines represent the ciliated bands ; and the shading the space between
the prae-oral and the post-oral bands.
 
m. mouth; an. anus.
 
The changes by which the Bipinnaria or Brachiolaria becomes
converted into the adult starfish are very much more complicated
than those which take place in Holothurians. For an accurate
knowledge of them we are largely indebted to Alex. Agassiz
(No. 543). The development of the starfish takes place entirely
at the posterior end of the larva close to the stomach.
 
On the right and dorsal side of the stomach, and externally
to the rig/it peritoneal space, are formed five radially situated
calcareous rods arranged in the form of a somewhat irregular
pentagon. The surface on which they are deposited has a
spiral form, and constitutes together with its calcareous rods, the
 
 
 
ECHINODERMATA. 559
 
 
 
abactinal or dorsal surface of the future starfish. Close to its
dorsal, i.e. embryonic dorsal, edge lies the dorsal pore of the
water-vascular system (madreporic canal), and close to its ventral
edge the anus. On the left and ventral side of the stomach is
placed the water-vascular rosette, the development of which was
described on p. 549. It is situated on the actinal or ventral surface
of the future starfish, and is related to the left peritoneal vesicle.
 
Metschnikoff (No. 560) and Agassiz (No. 543) differ slightly as to the
constitution of the water- vascular rosette. The former describes and figures
it as a completely closed rosette, the latter states that ' it does not form a
completely closed curve but is always open, forming a sort of twisted
crescent-shaped arc.'
 
The water-vascular rosette is provided with five lobes, corresponding to which are folds in the larval skin, and each lobe
corresponds to one of the calcareous plates developed on the
abactinal disc. The plane of the actinal surface at first meets
that of the abactinal at an acute or nearly right angle. The two
surfaces are separated by the whole width of the stomach. The
general appearance of the larva from the ventral surface after
the development of the water-vascular rosette (i) and abactinal
disc (A) is shewn in fig. 260.
 
As development proceeds the abactinal surface becomes a
firm and definite disc, owing to the growth of the original
calcareous spicules into more or less definite plates, and to the
development of five fresh plates nearer the centre of the disc and
interradial in position. Still later a central calcareous plate
appears on the abactinal surface, which is thus formed of a
central plate, surrounded by a ring of five interradial plates, and
then again by a ring of five radial plates. The abactinal disc
now also grows out into five short processes, separated by five
shallow notches. These processes are the rudiments of the five
arms, and each of them corresponds to one of the lobes of the
water-vascular rosette. A calcareous deposit is formed round
the opening of the water-vascular canal, which becomes the
madreporic tubercle 1 . At about this stage the absorption of the
larval appendages takes place. The whole anterior part of the
 
1 The exact position of the madreporic tubercle in relation to the abactinal plates
does not seem to have been made out. It might have been anticipated that it would
be placed in one of the primary interradial plates, but this does not seem to be the
case. The position of the anus is also obscure.
 
 
 
5 6o
 
 
 
BIPINNARIA.
 
 
 
 
larva with the great prae-oral lobe has hitherto remained
unchanged, but now it contracts and undergoes absorption, and
becomes completely withdrawn into the disc of the future starfish.
The larval mouth is transported into
the centre of the actinal disc. In the
larvae observed by Agassiz and Metschnikoff nothing was cast off, but the
whole absorbed.
 
According to M tiller and Koren and
Danielssen this is not the case in the larva
observed by them, but part of the larva is
thrown off, and lives for some time independently.
 
After the absorption of the larval
appendages the actinal and abactinal
surfaces of the young starfish approach
each other, owing to the flattening of
the stomach ; at the same time they
lose their spiral form, and become flat
discs, which fit each other. Each of
the lobes of the rosette of the watervascular system becomes one of the
radial water-vascular canals. It first
becomes five-lobed, each lobe forming
a rudimentary tube foot, and on each ^ d ctinal disc of youn Aste '
side of the middle lobe two fresh ones
 
next spring out, and so on in succession. The terminal median
lobe forms the tentacle at the end of the arm, and the eye is
developed at its base. The growth of the water-vascular canals
keeps pace with that of the arms, and the tube feet become
supported at their base by an ingrowth of calcareous matter.
The whole of the calcareous skeleton of the larva passes directly
into that of the adult, and spines are very soon formed on the
plates of the abactinal surface. The original radial plates,
together with the spines which they have, are gradually pushed
outwards with the growth of the arms by the continual addition
of fresh rows of spines between the terminal plate and the plate
next to it. It thus comes about that the original radial plates
persist at the end of the arms, in connection with the unpaired
 
 
 
FIG. 260. BIPINNARIA
LARVA OF AN ASTEROID. (From
Gegenbaur ; after Miiller.)
 
b. mouth ; a. anus ; h. madreporic canal ; t. ambulacral
rosette ; c . stomach ; d. g. e.
etc. arms of Bipinnaria ; A.
 
 
 
ECHINODERMATA. 561
 
 
 
tentacles which form the apex of the radial water-vascular
tubes.
 
It has already been mentioned that according to Metschnikoff (No. 560)
a new oesophagus is formed which perforates the water-vascular ring, and
connects the original stomach with the original mouth. Agassiz (No. 543)
maintains that the water-vascular ring grows round the primitive oesophagus.
He says " During the shrinking of the larva the long oesophagus becomes
" shortened and contracted, bringing the opening of the mouth of the larva
" to the level of the opening of the oesophagus, which eventually becomes
"the true mouth of the starfish." The primitive anus is believed by
Metschnikoff to disappear, but by Agassiz to remain. This discrepancy
very possibly depends upon these investigators having worked at different
species.
 
There is no doubt that the whole of the larval organs, with
the possible exception of the oesophagus, and anus (where absent
in the adult), pass directly into the corresponding organs of the
starfish and that the prae-oral part of the body and arms of the
larva are absorbed and not cast off.
 
In addition to the Bipinnarian type of Asteroid larva a series of other
forms has been described by Miiller (No. 561), Sars, Keren, and Danielssen
(No. 554) and other investigators, which are however very imperfectly
known. The best-known form is one first of all discovered by Sars in
Echinaster Sarsii, and the more or less similar larvae subsequently investigated by Agassiz, Busch, Miiller, Wyville Thomson, etc. of another species
of Echinaster and of Asteracanthion. These larvae on leaving the egg have
an oval form, and are uniformly covered by cilia. Four processes (or in
Agassiz' type one process) grow out from the body ; by these the larvae fix
themselves. In the case of Echinaster the larvae are fixed in the ventral
concavity of the disc of the mother, between the five arms, where a temporary brood-pouch is established. The main part of the body is converted
directly into the disc of the young starfish, while the four processes come to
spring from the ventral surface, and are attached to the water- vascular ring.
Eventually they atrophy completely. Of the internal structure but little is
known ; till the permanent mouth is formed, after the development of the
young starfish is pretty well advanced, the stomach has no communication
with the exterior.
 
A second abnormal type of development is presented by the embryo of
Pteraster miliaris, as described by Koren and Danielssen 1 . The larvae to
the number of eight to twenty develop in a peculiar pouch on the dorsal
surface of the body. The early stages are not known, but in the later ones
the whole body assumes a pentagonal appearance with a mouth at one edge
 
1 The following statements are taken from the abstract in Bronn's Thierreichs.
B. II. 36
 
 
 
5 62
 
 
 
OPHIUROID PLUTEUS.
 
 
 
of the disc. At a later stage the anus is formed on the dorsal side of an arm
opposite the mouth. The stomach is surrounded by a water-vascular ring,
from which the madreporic canal passes to the dorsal surface, but does not
open. At a later stage the embryonic mouth and anus vanish, to be replaced
by a permanent mouth and anus in the normal positions.
 
A third, and in some respects very curious, form is a worm like larva of
Miiller, which is without bands of cilia. The dorsal surface of the youngest
larva is divided by transverse constrictions into five segments. On the
under side of the first of these is a five-lobed disc, each lobe being provided
with a pair of tube feet.
 
At a later period only three segments are visible on the dorsal surface,
but the ventral surface has assumed a pentagonal aspect. The later stages
are not known.
 
Ophiuroidea. The full-grown larva of the Ophiuroids is
known as a Pluteus. It commences with the usual more or less
spherical form ; from this it passes to a form closely resembling
 
 
 
 
FIG. 261. DIAGRAMMATIC FIGURES SHEWING THE EVOLUTION OK AN OPHIUROID PLUTEUS FROM A SIMPLE ECHINODERM LARVA. (Copied from Miiller.) The
calcareous skeleton is not represented.
 
///. mouth; an. anus; d. anterior arms; d'. lateral arms; e'. posterior arms; tf.
anterolateral arms.
 
that of Auricularia with a rounded dorsal surface, and a flattened
ventral one. Soon however it becomes distinguished by the
growth of a post-anal lobe and the absence of a prae-oral lobe
(fig. 261 B). The post-anal lobe forms the somewhat rounded
apex of the body. In front of the mouth, and between the
mouth and anus, arise the anal and oral ciliated ridges, which
soon become continued into a single longitudinal ciliated ring.
At the same time the body becomes prolonged into a series of
 
 
 
ECHINODERMATA.
 
 
 
563
 
 
 
processes along the ciliated band, which is continued to the
extremity of each. The primitive ciliated ring never becomes
broken up into two or more rings. A ciliated crown is usually
developed at the extremity of the post-anal lobe. The arms are
arranged in the form of a ring surrounding the mouth, and are
all directed forwards.
 
The first arms to appear are two lateral ones, which usually remain the
most conspicuous (fig. 261 B and C, cf\ Next arises a pair on the sides of
the mouth, which may be called the mouth or anterior arms (C, d}. A pair
ventral to and behind the lateral arms is then formed, constituting the
posterior arms (D, e'\ and finally a pair between the lateral arms and the
anterior, constituting the anterolateral arms (D,^).
 
The concave area between the arms forms the greater part of
the ventral surface of the body. Even before the appearance of
any of the arms, and before the formation of the mouth, two
calcareous rods are formed, which meet behind at the apex of
the post-anal lobe, and are continued as a central support into
each of the arms as they are successively formed. These rods
are shewn at their full development in fig. 262. The important
points which distinguish a Pluteus
larva from the Auricularia or
Bipinnaria are the following :
 
(i) The presence of the postanal lobe at the hind end of the
body. (2) The slight development of a prae-oral lobe. (3) The
provisional calcareous skeleton in
the larval arms.
 
Great variations are presented
in the development of the arms
and provisional skeleton. The
presence of lateral arms is however
a distinctive characteristic of the
Ophiuroid Pluteus. The other
arms may be quite absent, but
the lateral arms never.
 
The formation of the permanent Ophiuroid takes place in
much the same way as in the Asteroidea.
 
36-2
 
 
 
 
FIG. 262.
OPHIUROID.
after Miiller.)
 
 
 
PLUTEUS LARVA OF AN
(From Gegenbaur ;
 
 
 
A. rudiment of young Ophiuroid ;
(?. lateral arms; d. anterior arms;
e . posterior arms.
 
 
 
564
 
 
 
OPHIUROID PLUTEUS.
 
 
 
There is formed (fig. 262) on the right and dorsal side of stomach the
abactinal disc supported by calcareous plates, at first only five in number
and radial in position 1 . The disc is at first not symmetrical, but becomes so
at the time of the resorption of the larval arms. It grows out into five
processes the five future rays. The original five radial plates remain as the
terminal segments of the adult rays, and new plates are always added
between the ultimate and penultimate plate (Mu'ller), though it is probable
that in the later stages fresh plates are added in the disc.
 
The ventral surface of the permanent Ophiuroid is formed by the concave
surface between the mouth and anus. Between this and the stomach is
 
 
 
 
FIG. 263. DIAGRAMMATIC FIGURES SHEWING THE EVOLUTION OF ECHINOID
PLUTEI. (Copied from Miiller.) The calcareous skeleton is not represented. E.
Pluteus of Spatangus.
 
m. mouth; an. anus; d. anterior arms; d' . point where lateral arms arise in the
Ophiuroid Pluteus; e. anterointernal arms; e. posterior arms; g'. anterolateral arms;
g. anteroexternal arms.
 
situated the water-vascular ring. It is at first not closed, but is horseshoeshaped, with five blind appendages (fig. 262). It eventually grows round
the cesophagus, which, together with the larval mouth, is retained in the
adult. The five blind appendages become themselves lobed in the same
way as in Asterias, and grow out along the five arms of the disc and become
the radial canals and tentacles. All these parts of the water-vascular system
are of course covered by skin, and probably also surrounded by mesoblast
cells, in which at a later period the calcareous plates which lie ventral to the
radial canal are formed. The larval anus disappears. As long as the larval
appendages are not absorbed the ventral and dorsal discs of the permanent
Ophiuroid fit as little as in the case of the Brachiolaria, but at a certain
period the appendages are absorbed. The calcareous rods of the larval arms
 
1 Whether interradial plates are developed as in Asterias is not clear. They seem
to be found in Ophiopholis bellis, Agassiz, but have not been recognised in other
forms (vide Carpenter, No. 548, p. 369).
 
 
 
ECHINODERMATA. 565
 
 
 
break up, the arms and anal lobe become absorbed, and the dorsal and
ventral discs, with the intervening stomach and other organs, are alone left.
After this the discs fit together, and there is thus formed a complete young
Ophiuroid.
 
The whole of the internal organs of the larva (except the anus), including
the mouth, cesophagus, the body cavity, etc. are carried on directly into the
adult.
 
The larval skeleton is, as above stated, absorbed.
 
The viviparous larva of Amphiura squamata does not differ very greatly
from the larvae with very imperfect arms. It does not develop a distinct
ciliated band, and the provisional skeleton is very imperfect. The absence
of these parts, as well as of the anus, mentioned on p. 549, may probably be
correlated with the viviparous habits of the larva. With reference to the
passage of this larva into the adult there is practically nothing to add to
what has just been stated. When the development of the adult is fairly
advanced the part of the body with the provisional skeleton forms an
elongated rod-like process attached to the developing disc. It becomes
eventually absorbed.
 
Echinoidea. The Echinus larva (fig. 263} has a Pluteus
form like that of the Ophiuroids, and in most points, such as the
 
 
 
 
 
FIG. 264. Two LARV/E OF STRONGYLOCENTRUS. (From Agassiz.)
m. mouth; a. anus; o. cesophagus; d. stomach; c. intestine; '. and v. ciliated
ridges; iv. water- vascular tube; r. calcareous rods.
 
presence of the anal lobe, the ciliated band, the provisional
skeleton, etc., develops in the same manner. The chief difference
between the two Pluteus forms concerns the development of the
lateral arms. These, which form the most prominent arms in
the Ophiuroid Pluteus, are entirely absent in the Echinoid
 
 
 
5 66
 
 
 
ECHINOID PLUTEUS.
 
 
 
Pluteus, which accordingly has, as a rule, a much narrower form
than the Ophiuroid Pluteus.
 
A pair of ciliated epaulettes on each side of and behind the
ciliated ring is very characteristic of some Echinoid larvae.
They are originally developed from the ciliated ring (fig. 266 A
 
 
 
 
 
FIG. 265. LATERAL AND VENTRAL VIEW OF A LARVA OF STRONGYLOCENTRUS.
 
(From Agassiz.) General references as in fig. 264.
 
b. dorsal opening of madreporic canal; e '. posterior arms ; e'". anterior arms;
f lV . anterointernal arms.
 
and B, z>"). The presence of three processes from the anal lobe
supported by calcareous rods is characteristic of the Spatangoid
Pluteus (fig. 263 E).
 
The first two pairs of arms to develop, employing the same names as in
Ophiuroids, are the anterior attached to the oral process (fig. 263 C, d] and
the posterior pair (*?') A pair of anterolateral arms next becomes developed
(j^). A fourth pair (not represented in Ophiuroids) appears on the inner
side of the anterior pair forming an anterointernal pair (e}, and in the
Spatangoid Pluteus a fifth pair may be added on the external side of the
anterior pair forming an anteroexternal pair (g).
 
Each of the first-formed paired calcareous rods is composed of three
processes, two of which extend into the anterior and posterior arms ; and the
third and strongest passes into the anal lobe, and there meets its fellow
(fig. 265). A transverse bar in front of the arms joins the rods of the two
sides meeting them at the point where the three processes diverge. The
process in the anterolateral arm (fig. 266 B) is at first independent of this
system of rods, but eventually unites with it. Although our knowledge of
 
 
 
ECHINODERMATA. 567
 
 
 
the Pluteus types in the different groups is not sufficient to generalise with
great confidence, a few points seem to have been fairly determined 1 . The
Plutei of Strongylocentrus (figs. 266 and 267) and Echinus have eight arms
and four ciliated epaulettes. The only Cidaris-like form, the Pluteus of
which is known, is Arbacia : it presents certain peculiarities. The anal lobe
develops a pair of posterior (auricular) appendages, and the ciliated ring,
besides growing out into the normal eight appendages, has a pair of short
blunt anterior and posterior lobes. An extra pair of non-ciliated accessory
mouth arms appears also to be developed. Ciliated epaulettes are not
present. So far as is known the Clypeastroid larva is chiefly characterized
by the round form of the anal lobe. The calcareous rods are latticed. In the
Pluteus of Spatangoids there are (fig. 263) five pairs of arms around the
mouth pointing forwards, and three arms developed from the anal lobe
pointing backwards. One of these is unpaired, and starts from the apex of
the anal lobe. All the arms have calcareous rods which, in the case of the
posterior pair, the anterolateral pair, and the unpaired arm of the anal lobe,
are latticed. Ciliated epaulettes are not developed.
 
Viviparous larvae of Echinoids have been described by Agassiz 2 .
 
The development of the permanent Echinus has been chiefly worked out
by Agassiz and Metschnikoff.
 
In the Pluteus of Echinus lividus the first indication of the adult arises,
when three pairs of arms are already developed, as an invagination of the
skin on the left side, between the posterior and anterolateral arms, the
bottom of which is placed close to the water-vascular vesicle (fig. 266 B, u/\
The base of this invagination becomes very thick, and forms the ventral disc
of the future Echinus. The parts connecting this disc with the external
skin become however thin, and, on the narrowing of the external aperture of
invagination and the growth of the thickened disc, constitute a covering for
the disc, called by Metschnikoff the amnion. The water- vascular vesicle
adjoining this disc grows out into five processes, forming as many tube feet,
which cause the surface of the involuted disc to be produced into the same
number of processes. The external opening of the invagination of the disc
never closes, and after the development of the tube feet begins to widen
again, and the amnion to atrophy. Through the opening of the invagination
the tube feet now project. The dorsal and right surface of the Pluteus,
which extends so as to embrace the opening of the madreporic canal and
the anus, forms the abactinal or dorsal surface of the future Echinus
(fig. 267, a). This disc fits on to the actinal invaginated surface which arises
on the left side of the Pluteus. On the right surface of the larva (dorsal of
permanent Echinus) two pedicellariae appear, and at a later period spines
are formed, which are at first arranged in a ring-like form round the edge of
the primitively flat test. While these changes are taking place, and the two
surfaces of the future Echinus are gradually moulding themselves so as to
 
1 Vide especially Muller, Agassiz, and Metschnikoff.
 
2 For viviparous Echini vide Agassiz, Proc. Amer. Acad. 1876.
 
 
 
5 68
 
 
 
ECHINOID PLUTEUS.
 
 
 
form what is obviously a young Echinus, the arms of the Pluteus with their
contained skeleton have been gradually undergoing atrophy. They become
irregular in form, their contained skeleton breaks up into small pieces, and
they are gradually absorbed.
 
The water-vascular ring is from the first complete, so that, as in
Asterias, it is perforated through the centre by a new oesophagus. According
 
 
 
 
 
FIG. 266. SIDE AND DORSAL VIEW OF A LARVA OF STRONGYLOCENTRUS.
 
(From Agassiz.) General reference letters as in figs. 264 and 265.
e" . anterolateral arms; v" '. ciliated epaulettes; ?&'. invagination to form the disc
of Echinus.
 
to Agassiz the first five tentacles or tube feet grow into the radial canals,
and form the odd terminal tentacles exactly as in Asterias 1 . Spatangus
only differs in development from Echinus in the fact that the opening of the
invagination to form the ventral disc becomes completely closed, and that
the tube feet have eventually to force their way through the larval epidermis
of the amnion, which is ruptured in the process and eventually thrown
off.
 
Crinoidea. The larva of Antedon, while still within the
egg-shell, assumes an oval form and uniform ciliation. Before it
 
1 Gotte (No. 549) supported by Muller's and Krohn's older, and in some points
extremely erroneous observations, has enunciated the view that the radial canals in
Echinoids and Holothuroids have a different nature from those in Asteroids and
Ophiuroids.
 
 
 
ECHINODERMATA.
 
 
 
569
 
 
 
becomes hatched the uniform layer of cilia is replaced by four
transverse bands of cilia, and a tuft of cilia at the posterior
extremity. In this condition it escapes from the egg-shell
 
 
 
 
FIG. 267. FULL-GROWN LARVA OF STRONGYLOCENTRUS. (From Agassiz.)
The figure shews the largely-developed abactinal disc of the young Echinus
enclosing the larval stomach. Reference letters as in previous figs.
 
(fig. 268 A), and becomes bilateral, owing to a flattening of the
ventral surface. On the flattened surface appears a ciliated
 
 
 
570
 
 
 
CRINOID LARVA.
 
 
 
depression corresponding in position with the now closed blastopore (vide p. 550). The third ciliated band bends forward
to pass in front of this (fig. 269). Behind the last ciliated band
there is present a small depression of unknown function, also
 
 
 
 
FIG. 768. THREB STAGES IN THE DEVELOPMENT OF ANTEDON (COMATULA.)
 
(From Lubbock; after Thomson.)
 
A. larva just hatched; B. larva with rudiment of the calcareous plates; C. Pentacrinoid larva.
 
 
 
ECHINODERMATA.
 
 
 
571
 
 
 
situated on the ventral surface. The posterior extremity of the
embryo elongates to form the rudiment of the future stem, and
a fresh depression, marking the position of the future mouth,
makes its appearance on the anterior and ventral part.
 
While the ciliated bands are still at their full development,
the calcareous skeleton of the future calyx makes its appearance
in the form of two rows, each of five plates, formed of a network
of spicula (figs. 268 B and 269). The plates of the anterior ring
are known as the orals, those of the posterior as the basals.
The former surround the left, i.e. anterior
peritoneal sack ; the latter the right, i.e.
posterior peritoneal sack. The two rows
of plates are at first not quite transverse,
but form two oblique circles, the dorsal
end being in advance of the ventral.
The rows soon become transverse, while
the originally somewhat ventral oral
surface is carried into the centre of the
area enclosed by the oral plates.
 
By the change in position of the
original ventral surface relatively to the
axis of the body, the bilateral symmetry
of the larva passes into a radial symmetry. While the first skeletal elements
of the calyx are being formed, the
skeleton of the stem is also established.
The terminal plate is first of all established, then the joints, eight at first, of
the stem. The centro-dorsal plate is
stated by Thomson to be formed as the
uppermost joint of the stem 1 . The larva, after the completion
of the above changes, is shewn in fig. 268 B, and somewhat more
diagrammatically in fig. 269.
 
After the above elements of the skeleton have become established the ciliated bands undergo atrophy, and shortly after
1 Gotte (No. 549) on the other hand holds that the centro-dorsal plate is developed
by the coalescence of a series of at first independent rods, which originate simultaneously with, and close to, the lower edges of the basals, and that it is therefore
similar in its origin to the basals.
 
 
 
 
FIG. 269. LARVA OF
ANTEDON WITH RUDIMENTS
OF CALCAREOUS SKELETON.
(From Carpenter; after
Thomson.)
 
i. Terminal plate at the
end of the stem ; 3. basals ;
or. orals ; bl. position of blastopore.
 
 
 
572
 
 
 
CRINOID LARVA.
 
 
 
wards the larva becomes attached by the terminal plate of its
stem. It then passes into the Pentacrinoid stage! The larva in
this stage is shewn in fig. 268 C and fig. 270. New joints are
added at the upper end of the stem next the calyx, and a new
element the radials makes its appearance as a ring of five
small plates, placed in the space between the basals and orals,
and in the intervals alternating with them
(fig. 270, 4). The roof of the oral vestibule (vide fig. 253 and p. 551) has in
the meantime become ruptured ; and
the external opening of the mouth thus
becomes established. Surrounding the
mouth are five petal-like lobes, each of
them supported by an oral plate (fig.
268 C). In the intervals between them
five branched and highly contractile tentacles, which were previously enclosed
within the vestibule, now sprout out :
they mark the position of the future
radial canals, and are outgrowths of the
water-vascular ring. At the base of each
of them a pair of additional tentacles is
soon formed. Each primary tentacle corresponds to one of the radials. These
latter are therefore, as their name implies,
radial in position; while the basals and
orals are interradial. In addition to the
contractile radial tentacles ten non-contractile tentacles, also diverticula of the
water- vascular ring, are soon formed, two
for each interradius.
 
In the course of the further development the equatorial space between the FlG - 2 7<>. YOUNG PEN
. TACRINOID LARVA OF AN
 
orals and the basals enlarges, and gives TEDON. (From Carpenter ;
rise to a wide oral disc, the sides of which after w >' ville Thom s"-)
 
- , , . ... . i. terminal plate of stem;
 
are formed by the radials resting on the c d. centro-donal plate; 3 .
basals; while in the centre of it are bftsals J 4- radials; or. orals.
placed the five orals, each with its special lobe.
 
The anus, which is formed on the ventral side in the position
 
 
 
 
ECHINODERMATA. 573
 
 
 
of the blastopore (p. 551), becomes surrounded by an anal plate,
which is interradial in position, and lies on the surface of the
oral disc between the orals and radials. On the oral plate in
the next interradius is placed the opening of a single funnel
leading into the body cavity, which Ludwig regards as equivalent to the opening of the madreporic canal (vide p. 55 1) 1 .
 
From the edge of the vestibule the arms grow out, carrying
with them the tentacular prolongation of the water-vascular ring.
Two additional rows of radials are soon added.
 
The stalked Pentacrinoid larva becomes converted, on the
absorption of the stalk, into the adult Antedon. The stalk is
functionally replaced by a number of short cirri springing from
the centro-dorsal plate. The five basals coalesce into a single
plate, known as the rosette, and the five orals disappear, though
the lobes on which they were placed persist. In some stalked
forms, e.g. Rhizocrinus Hyocrinus, the orals are permanently
retained. The arms bifurcate at the end of the third radial, and
the first radial becomes in Antedon rosacea (though not in all
species of Antedon) concealed from the surface by the growth of
the centro-dorsal plate. An immense number of funnels, leading
into the body cavity, are formed in addition to the single one
present in the young larva. These are regarded by Ludwig as
equivalent to so many openings of the madreporic canal ; and
there are developed, in correspondence with them, diverticula of
the water-vascular ring.
 
Comparison of Echinoderm Larvce and General Conclusions.
 
In any comparison of the various types of Echinoderm larvae
it is necessary to distinguish between the free-swimming forms,
and the viviparous or fixed forms. A very superficial examination suffices to shew that the free-swimming forms agree very
much more closely amongst themselves than the viviparous
 
1 I have made no attempt to discuss the homologies of the plates of the larval
Echinodermata because the criteria for such a discussion are still in dispute. The
suggestive memoirs of P. H. Carpenter (No. 548) on this subject may be consulted by
the reader. Carpenter attempts to found his homologies on the relation of the plates
to the primitive peritoneal vesicles, and I am inclined to believe that this method of
dealing with these homologies is the right one. Ludwig (No. 559) by regarding the
opening of the madreporic canal as a fixed point has arrived at very different results.
 
 
 
574
 
 
 
COMPARISON OF ECHINODERM LARV.-E.
 
 
 
forms. We are therefore justified in concluding that in the
viviparous forms the development is abbreviated and modified.
 
All the free forms are nearly alike in their earliest stage after
the formation of the archenteron. The surface between the
anus and the future mouth becomes flattened, and (except in
Antedon, Cucumaria, Psolinus, etc. which practically have an
abbreviated development like that of the viviparous forms) a
ridge of cilia becomes established in front of the mouth, and a
second ridge between the mouth and the anus. This larval
form, which is shewn in fig. 264 A, is the type from which the
various forms of Echinoderm larvae start.
 
In all cases, except in Bipinnaria, the two ciliated ridges
soon become united, and constitute a single longitudinal postoral ciliated ring.
 
The larvae in their further growth undergo various changes,
and in the later stages they may be divided into two groups :
 
(1) The Pluteus larva of Echinoids and Ophiuroids.
 
(2) The Auricularia (Holothuroids) and Bipinnaria (Asteroids) type.
 
The first group is characterized by the growth of a number
of arms more or less surrounding the mouth, and supported
by calcareous rods. The ciliated band retains its primitive
condition as a simple longitudinal band throughout larval life.
There is a very small prae-oral lobe, while an anal lobe is very
largely developed.
 
The Auricularia and Bi- A. B
 
pinnaria resemble each other
in shape, in the development
of a large prae-oral lobe, and
in the absence of provisional
calcareous rods ; but differ in
the fact that the ciliated band
is single in Auricularia (fig
271 A), and is double in Bipinnaria (fig. 271 B).
 
TheBipinnarialarvashews
 
THUROID. B. THE LARVA OF AN ASTEa great tendency to develop RIAS.
 
soft arms; while in the Auri- . ' mouth; st. stomach; a. anus; I.e.
, . ,_, , *_ 1-1- primitive longitudinal ciliated band; pr.c.
 
cularia the longitudinal ciliat- p r3 e-oral ciliated band.
 
 
 
 
FlG
 
 
THE LARVA OF A
 
 
 
ECHINODERMATA. 575
 
 
 
ed band breaks up into a number of transverse ciliated bands.
This condition is in .some instances reached directly, and such
larvae undoubtedly approximate to the larvae of Antedon, in
which the uniformly ciliated condition is succeeded by one with
four transverse bands, of which one is prae-oral.
 
All or nearly all Echinoderm larvae are bilaterally symmetrical,
and since all Echinodermata eventually attain a radial symmetry, a change necessarily takes place from the bilateral to the
radial type.
 
In the case of the Holothurians and Antedon, and generally
in the viviparous types, this change is more or less completely
effected in the embryonic condition ; but in the Bipinnaria and
Pluteus types a radial symmetry does not become apparent till
after the absorption of the larval appendages. It is a remarkable fact, which seems to hold for the Asteroids, Ophiuroids, Echinoids, and Crinoids, that the dorsal side of the larva is
not directly converted into the dorsal disc of the adult; but
the dorsal and right side becomes the adult dorsal or abactinal
surface, while the ventral and left becomes the actinal or ventral
surface.
 
It is interesting to note with reference to the larvae of the
Echinodermata that the various existing types of larvae must
have been formed after the differentiation of the existing groups
of the Echinodermata ; otherwise it would be necessary to adopt
the impossible position that the different groups of Echinodermata were severally descended from the different types of larvae.
The various special appendages, etc. of the different larvae have
therefore a purely secondary significance; and their atrophy
at the time of the passage of the larva into the adult, which
is nothing else but a complicated metamorphosis, is easily explained.
 
Originally, no doubt, the transition from the larva to the
adult was very simple, as it is at present in most Holothurians ;
but as the larvae developed various provisional appendages, it
became necessary that these should be absorbed in the passage
to the adult state.
 
It would obviously be advantageous that their absorption
should be as rapid as possible, since the larva in a state of
transition to the adult would be in a very disadvantageous
 
 
 
576 COMPARISON OF ECHINODERM
 
position. The rapid metamorphosis, which we find in Asteroids,
Ophiuroids, and Echinoids in the passage from the larval to the
adult state, has no doubt arisen for this reason.
 
In spite of the varying provisional appendages possessed by
Echinoderm larvae it is possible, as stated above (p. 574), to
recognise a type of larva, of which all the existing Echinoderm
larval forms are modifications. This type does not appear to
me to be closely related to that of the larvae of any group
described in the preceding pages. It has no doubt certain
resemblances to the trochosphere larva of Chaetopoda, Mollusca,
etc., but the differences between the two types are more striking
than the resemblances. It firstly differs from the trochosphere
larva in the character of the ciliation. Both larvae start from the
uniformly ciliated condition, but while the prae-oral ring is almost
invariable, and a peri-anal ring very common in the trochosphere;
in the Echinoderm larva such rings are rarely found ; and even
when present, i.e. the prae-oral ring of Bipinnaria and the terminal
though hardly peri-anal patch of Antedon, do not resemble
closely the more or less similar structures of the trochosphere.
The two ciliated ridges (fig. 264 A) common to all the Echinoderm larvae, and subsequently continued into a longitudinal ring,
have not yet been found in any trochosphere. The transverse
ciliated rings of the Holothurian and Crinoid larvae are of no
importance in the comparison between the trochosphere larvae
and the larvae of Echinodermata, since such rings are frequently
secondarily developed. Cf. Pneumodermon and Dentalium amongst Mollusca.
 
In the character of the prae-oral lobe the two types again
differ. Though the prae-oral lobe is often found in Echinoderm
larvae it is never the seat of an important (supra-oesophageal)
ganglion and organs of special sense, as it invariably is in the
trochosphere.
 
Nothing like the vaso-peritoneal vesicles of the Echinoderm
larvae has been found in the trochosphere ; nor have the characteristic trochosphere excretory organs been found in the Echinoderm larvae.
 
The larva which most nearly approaches those of the Echinodermata is the larva of Balanoglossus described in the next
chapter.
 
 
 
ECHINODERMATA. 577
 
 
 
BIBLIOGRAPHY.
 
(542) Alex. Agassiz. Revision of the Echini. Cambridge, U.S. 1872 74.
 
(543) Alex. Agassiz. " North American Starfishes." Memoirs of the Museum
of Comparative Anatomy and Zoology at Harvard College, Vol. v., No. i. 1877
(originally published in 1864).
 
(544) J. Barrois. " Embryogenie de 1'Asteriscus verruculatus " Journal dc
VAnat. et Phys. 1879.
 
(545) A. Baur. Beitrdge zur Naturgeschichte d. Synapta digitata. Dresden,
1864.
 
(546) H. G. Bronn. Klassen u. Ordnungen etc. Strahlenthiere, Vol. II. 1860.
 
(547) W. B. Carpenter. "Researches on the structure, physiology and development of Antedon." Phil. Trans. CLVI. 1866, and Proceedings of the Roy. Soc.,
No. 166. 1876.
 
(548) P. H. Carpenter. " On the oral and apical systems of the Echinoderms."
Quart. J. of Micr. Science, Vol. xvm. and xix. 18789.
 
(549) A. Gotte. " Vergleichende Entwicklungsgeschichte d. Comatula mediterranea." Arch, fur micr. Anat., Vol. xn. 1876.
 
(550) R. Greeff. "Ueber die Entwicklung des Asteracanthion rubens vom Ei
bis zur Bipinnaria u. Brachiolaria." Schriften d. Gesellschaft zur Beforderung d. gesammten Natunvissenschaften zu Marburg, Bd. xn. 1876.
 
(551) R. Greeff. "Ueber den Bau u. die Entwicklung d. Echinodermen." Sitz.
d. Gesell. z. Beforderung d. gesam. Naturwiss. zu Marburg, No. 4. 1879.
 
(552) T. H. Huxley. "Report upon the researches of Miiller into the anat.
anddevel. of the Echinoderms." Ann. and Mag. of Nat. Hist., 2nd Ser., Vol. vin.
1851.
 
(553) Koren and Danielssen. "Observations sur la Bipinnaria asterigera.
Ann. Scien. Nat., Ser. in., Vol. vii. 1847.
 
(554) Koren and Danielssen. "Observations on the development of the Starfishes." Ann. and Mag. of Nat. Hist., Vol. XX. 1857.
 
(555) A. Kowalevsky. " Entwicklungsgeschichte d. Holothurien. " Mhn.Ac.
Petersbourg, Ser. VII., Tom. XL, No. 6.
 
(556) A. Krohn. "Beobacht. a. d. Entwick. d. Holothurien u. Seeigel."
Miillers Archiv, 1851.
 
(557) A. Krohn. "Ueb. d. Entwick. d. Seesterne u. Holothurien." Miillcr's
Archiv, 1853.
 
(558) A. Krohn. "Beobacht. lib. Echinodermenlarven." Mailer's Archiv,
1854.
 
(559) H. Ludwig. "Ueb. d. primar. Steinkanal d. Crinoideen, nebst vergl.
anat. Bemerk. lib. d. Echinodermen." Zeit.f. wiss. ZooL, Vol. xxxiv. 1880.
 
(560) E. Metschnikoff. "Studien iib. d. Entwick. d. Echinodermen u.
Nemertinen." Mem. Ac. Petersboiirg, Series vii., Tom. xiv., No. 8. 1869.
 
(561) 1 Joh. Miiller. "Ueb. d. Larven u. d. Metamorphosed. Echinodermen."
Abhandlungen d. Berlin. Akad. (Five Memoirs), 1848, 49, 50, 52 (two Memoirs).
 
(562) Joh. Mtiller. "Allgemeiner Plan d. Entwicklung d. Echinodermen."
Abhandl. d. Berlin. Akad., 1853.
 
1 The dates in this reference are the dates of publication.
B. II. 37
 
 
 
578 BIBLIOGRAPHY.
 
 
 
(563) E. Selenka. "Zur Entwicklung d. Holothurien." Zeit. f. wiss. Zool.,
Bd. xxvii. 1876.
 
(564) E. Selenka. "Keimblatter u. Organanlage bei Echiniden." Zeit.f.-wiss.
Zool., Vol. xxxin. 1879.
 
(565) Sir Wyville Thomson. "On the Embryology of the Echinodermata."
Natural History Review, 1 864.
 
(566) Sir Wyville Thomson. "On the Embryogeny of Antedon rosaceus."
Phil. Trans. 1865.
 
 
 
CHAPTER XXI.
 
 
 
ENTEROPNEUSTA.
 
 
 
THE larva of Balanoglossus is known as Tornaria. The prselarval development is not known, and the youngest stage (fig.
272) so far described (Gotte, No. 569) has
many remarkable points of resemblance to
a young Bipinnaria.
 
A mouth (m\ situated on the ventral
surface, leads into an alimentary canal with
a terminal anus (an). A prae-oral lobe is
well developed, as in Bipinnaria, but there
is no post-anal lobe. The bands of cilia
have the same general form as in Bipinnaria. There is a prae-oral band, and a
longitudinal post-oral band ; and the two
bands nearly meet at the apex of the praeoral lobe (fig. 273). A contractile band
 
 
 
 
an
 
FIG. 272. EARLY
STAGE IN THE DEVELOPMENT OF TORNARIA.
(After Gotte.)
 
W. so-called watervascular vesicle developing as an outgrowth
of the mesenteron; m.
 
passes from the oesophagus to the apex of mouth; an. anus,
the prae-oral lobe, and a diverticulum (fig. 272, W) from the
alimentary tract, directed towards the dorsal surface, is present.
Contractile cells are scattered in the space between the body
wall and the gut.
 
In the following stage (fig. 274 A) a conspicuous transverse
post-oral band of a single row of long cilia is formed, and the
original bands become more sinuous. The alimentary diverticulum of the last stage becomes an independent vesicle opening
by a pore on the dorsal surface (fig. 274 A, w). The contractile
cord is now inserted on this vesicle. Where this cord joins the
apex of the prae-oral lobe between the two anterior bands of
cilia a thickening of the epiblast (? a ganglion) has become
 
372
 
 
 
580
 
 
 
ENTEROPNEUSTA.
 
 
 
 
C.C.
 
 
 
an.
 
FIG. 273. YOUNG TORNARIA.
 
(After Miiller.)
 
m. mouth ; an. anus ; w. watervascular vesicle ; oc. eye-spots ; c.c.
contractile cord.
 
 
 
established, and on it are placed
two eye-spots (fig. 273 oc, and
fig. 274 A). A deep bay is
formed on the ventral surface of
the larva.
 
As the larva grows older the
original bands of cilia become
more sinuous, and a second
transverse band with small cilia
is formed (in the Mediterranean
larva) between the previous
transverse band and the anus.
The water-vascular vesicle is
prolonged into two spurs, one
on each side of the stomach.
A pulsating vesicle or heart is
also formed (fig. 274 B, ht), and arises, according to Spcngel
(No. 572), as a thickening of the epidermis.
It subsequently becomes enveloped in a
pericardium, and is
placed in a depression
in the water-vascular
vesicle. Two pairs of
diverticula, one behind
the other, grow out
(Agassiz, No. 568) from
the gastric region of
the alimentary canal.
The two parts of each
pair form flattened
compartments, which
together give rise to a
complete investment of
the adjoining parts of
the alimentary tract.
The two parts of each
coalesce, and thus form
 
 
 
 
FlG. 274. TWO STAGKS IN THK 1 >KY KI.< >I'M KN I
 
OF TORNARIA. (After Metschnikoff.)
 
The black lines represent the ciliated hands.
m. mouth; an. anus; br. branchial cleft; ///.
 
heart ; c. Ixxly cavity between splanchnic and
 
somatic mesoblast layers; 7.-'. watcr-vascvilar vesicle:
 
v. circular blood-vessel.
 
 
 
ENTEROPNEUSTA.
 
 
 
5 8l
 
 
 
a double-walled cylinder round the alimentary tract, but their
cavities remain separated by a dorsal and ventral septum.
 
Eventually (Spengel) the cavity of the anterior cylinder
forms the section of the body cavity in the collar of the adult,
and that of the posterior (fig. 274 B, c) the remainder of the
body cavity. The septa, separating the two halves of each,
remain as dorsal and ventral mesenteries.
 
The conversion of Tornaria (fig. 274 A) into Balanoglossus
(fig. 274 B) is effected in a few hours, and consists mainly in
certain changes in configuration, and in the disappearance of
the longitudinal ciliated band.
 
The body of the young Balanoglossus (fig. 274 B) is divided
into three regions (i) the proboscidian region, (2) the collar,
(3) the trunk proper. The proboscidian region is formed by the
elongation of the prae-oral lobe into an oval body with the eyespots at its extremity, and provided with strong longitudinal
muscles. The heart (hi) and water-vascular vesicle lie near its
base, but the contractile cord connected with the latter is no longer
present. The mouth is placed on
the ventral side at the base of the
prae-oral lobe, and immediately behind it is the collar. The remainder
of the body is more or less conical,
and is still girt with the larval
transverse ciliated band, which lies
in the middle of the gastric region
in the Mediterranean species, but
in the cesophageal region in the
American one.
 
The whole of the body, including
the proboscis, becomes richly ciliated.
 
One of the most important cha- S us WITH FOUR BRANCHIAL
racters of the adult Balanoglossus CLEFTS * (After Alex. Agossiz.)
 
r . m. mouth ; an. anus ; br. bran
consists in the presence of respira- chial cleft . hL heart ; IV. watertory structures comparable with the vascular vesicle,
vertebrate gill slits. The earliest traces of these structures
are distinctly formed while the larva is still in the Tornaria
 
 
 
 
FIG. 275. LATE STAGE IN THE
DEVELOPMENT OF BALANOGLOS
 
 
582 I'N I'KUOl'NKUSTA.
 
 
 
condition, as one pair of pouches from the oesophagus in the
Mediterranean species, and four pairs in the American one
(fig. 275, br).
 
In the Mediterranean Tornaria the two pouches meet the
skin dorsally, and in the young Balanoglossus (fig. 274 B, br)
acquire an external opening on the dorsal side. In the American
species the first four pouches are without external openings
till additional pouches have been formed. Fresh gill pouches
continue to be formed both in the American and probably
the Mediterranean species, but the conversion of the simple
pouches into the complicated gill structure of the adult
has only been studied by Agassiz (No. 568) in the American
species. It would seem in the first place that the structure of
the adult gill slits is much less complicated in the American than
in the Mediterranean species. The simple pouches of the young
become fairly numerous. They are at first circular ; they then
become elliptical, and the dorsal wall of each slit becomes folded ;
subsequently fresh folds are formed which greatly increase the
complexity of the gills. The external openings are not acquired
till comparatively late.
 
Our knowledge of the development of the internal organs, mainly
derived from Agassiz, is still imperfect. The vascular system appears early
in the form of a dorsal and a ventral vessel, both pointed, and apparently
ending blindly at their two extremities. The two spurs of the water-vascular
vesicle, which in the Tornaria stage rested upon the stomach, now grow
round the oesophagus, and form an anterior vascular ring, which Agassiz
describes as becoming connected with the heart, though it still communicates
with the exterior by the dorsal pore and seems to become connected with the
remainder of the vascular system. According to Spengel (No. 572) the
dorsal vessel becomes connected with the heart, which remains through life
in the proboscis : the cavity of the water-vascular vesicle forms the cavity of
the proboscis in the adult, and its pore remains as a dorsal (not, as usually
stated, ventral) pore leading to the exterior.
 
The eye-spots disappear.
 
Tornaria is a very interesting larval form, since it is intermediate in structure between the larva of an Echinoderm and
trochosphere type common to the Mollusca, Chxtopoda, etc.
The shape of the body especially the form of the ventral
depression, the character of the longitudinal ciliated band, the
structure and derivation of the water-vascular vesicle, and the
 
 
 
ENTEROPNEUSTA. 583
 
 
 
formation of the walls of the body cavity as gastric diverticula,
are all characters which point to a connection with Echinodcrm
larvae.
 
On the other hand the eye-spots at the end of the prae-oral
lobe 1 , the contractile band passing from the oesophagus to the
eye-spots (fig. 273), the two posterior bands of cilia, and the
terminal anus are all trochosphere characters.
 
The persistence of the prae-oral lobe as the proboscis is
interesting, as tending to shew that Balanoglossus is the surviving representative of a primitive group.
 
*
 
BIBLIOGRAPHY.
 
(567) A. Agassiz. "Tornaria." Ann. Lyceum Nat. Hist.\u\. New York,
1866.
 
(568) A. Agassiz. "The History of Balanoglossus and Tornaria." Mem.
Amer. Acad. of Arts and Stien., Vol. IX. 1873.
 
(569) A. Gotte. " Entwicklangsgeschichte d. Comatula Mediterranea." Archiv
fur mikr. Anat., Bd. xii., 1876, p. 641.
 
(570) E. Metschnikoff. " Untersuchungen iib d. Metamorphose, etc. (Tornaria)." Zeit.fiir wiss. ZooL, Bd. xx. 1870.
 
(571) J. M tiller. " Ueb. d. Larven u. Metamor. d. Echinodermen." Berlin
Akad., 1849 and 1850.
 
(572) J. W. Spengel. "Ban u. Entwicklung von Balanoglossus. Tagebl. d.
Naturf. Vers. Miinchen, 1877.
 
1 It would be interesting to have further information about the fate of the thickening of epiblast in the vicinity of the eye-spots. The thickening should by rights be the
supra-oesophageal ganglion, and it does not seem absolutely impossible that it may give
rise to the dorso-median cord in the region of the collar, which constitutes, according
to Spengel, the main ganglion of the adult.
 
 
 
INDEX.
 
 
 
Abdominalia, 459, 493, 499
 
Acanthocephala, 379
 
Acanthosoma, 473, 474, 475
 
Acarina, 444, 454
 
Accipenser, 102
 
Achaeta, 319
 
Achelia, 538
 
Achtheres percarum, 490
 
Acineta, 7, 8
 
Acraspeda, 152, 165, 167, 178, 179, 182,
 
185, 186
 
Actinia, 169, 171, 179
Actinophrys, 9
 
Actinotrocha, 315, 318, 363, 364
Actinozoa, 26, 102, 152, j66, 170, 171,
 
172, 176, 178, 179, 181, 182, 186
Actinula, 155
Aculeata, 421
^Egineta flavescens, 158
yEginidae, 156, 158
^Eginopsis Mediterranea, 158
/Equorea Mitrocoma, 182
Agalma, 163
Agelena, 436, 450
Agelena labyrinthica, 119, 438
Alciope, 74
Alcippidae, 499
Alcyonaria, 152
Alcyonidse, 167, 168
Alcyonidium mytili, 297, 300, 302
Alcyonium palmatum, 119, 148, 167, 182
Alima, 484, 486
Amoeba, 19, 20
Amphibia, 22, 54, 56, 59, 60, 63, 66, 74,
 
83, 102
 
Amphilina, 218
 
Amphioxus, 54, 56, 59, 61, 66, 93, 426
Amphipoda, 518
Amphiporus lactifloreus, 202
Amphistomum, 31
 
,, subclavatum, 205
 
Amphitrochae, 330
Amphiura squamata, 565
 
 
 
Anchorella, 108, 492, 520
 
Anelasma squalicola, 499
 
Anguillulidse, 371
 
Annelida, 14, 25, 98, 503, 525
 
Anodon, 37, 38, 39, 100, 107, 259, 260,
 
265, 266, 268
Anopla, 189, 202
Anura, 5
 
Antedon, 568, 573, 574
Aphides, 15, 16, 76, 79, 116, 428, 429
Aphrodite, 42
 
Apis, 402, 407, 408, 412, 413
Aplysia, 99, 226, 238, 252, 253
Aplysinidaa, 146
Apoda, 459, 493
Aptera, 395, 420
Apus, 1 6, 79, 460, 463
Arachnida, 22, 114, 119, 413, 4.51, 435,
 
444, 454, 455, 458, 537, 539
Arachnitis, 171
Araneina, 50, 51, 436
Arbacia, 567
Area, 38
Archigetes, 218
Archizosea gigas, 494
Arenicola, 42
 
Argiope, 311, 312, 315, 317
Argonauta, 247, 248
Argulus, 492
Armata, 355
Arthropoda, 12, 16, 18, 22, 75, 77,79, 83,
 
108, no, 221, 382, 383, 434, 448,503,
 
5 2 5> 534 54', 54 2
Articulata, 311, 313, 316, 317
Ascaridiae, 371
Ascaris nigrovenosa, 16, 82
 
,, lumbricoides, 375
Ascetta, 144
Ascidia canina, 53
Ascidians, 74, 102, 208, 426
Asellus aquaticus, 112,120, 516
Astacus, 66, 465, 477, 511, 512, 513,
 
525
 
 
 
586
 
 
 
INDKX.
 
 
 
Asteracanthion, 69, 70, 561
 
Asterias, 20, 68, 69, 71, 78, 80, 84, 549,
 
564
Asteroidea, 35, 36, 544, 549, 557, 563,
 
576
Astnea, 169
 
Astroides, 169
 
Atax Bonzi, 445
 
Atlanta, 231, 240
 
Atrochae, 330
 
Aurelia, 167
 
Auricularia, 553, 554, 562, 574
 
Autolytus cornutus, 319, 343
 
Aves, 56, 59, 61, 64, 107. 109
 
Axolotl, 1 6
 
Balanoglossus, 576, 579, 581
 
Balanus balanoides, 75, 493
 
Belemnites, 252, 253
 
Bipinnaria, 557, 563, 574, 576, 579
 
Blatta, 374, 395
 
Bojanus, organ of, 264, 282
 
Bonellia, 20, 43, 44, 98, 324, 355, 358,
 
359
Bothriocephalus salmonis, 211
 
,, proboscideus, 212
 
Brachiella, 492
Brachiolaria, 558, 564
Brachiopoda, 311, 317, 318
Brachyura, 466, 480, 483
Branchiobdella, 42, 43, 346
Branchiogasteropoda, 272
Branchiopoda, 79, 459, 523, 524
Branchipus, 463, 524
Branchiura, 459, 492
Branchionus urceolaris, 221
Braula, 396
Uuccinum, 237, 280
Bulimus citrinus, 229
Bunodes, 169, 171
Buthus, 431
 
Calcispongiae, 138, 148
 
Calopteryx, 402
 
Calycophoridce, 152, 159
 
Calyptoblastic Hydroids, 184, 185
 
Calyptraea, 223, 280
 
Campanularidse, 183, 184
 
Capitclla, 330, 332
 
Carabidae, 476
 
Carcinus Mcenas, 481, 483
 
Cardium, 260, 262
 
" pygmaeum, 262
 
Carinaria, 240
 
Caryophyllium, 168, 171
pea, 165, 167
 
Cecidomyia, 15, 79, 416, 417, 429
 
Cephalopoda, 20, 40, 41, 102, 108, 109,
135. "5. 240, 242, 244, 250, 252, 253,
270, 271, 272, 274, 279, 282, 287
 
Cephalothrix galatheae, 202
 
Ceratosponguc, 146
 
 
 
Cercariae, 207, 208, 209
 
Cerianthus, 168, 171
 
Cestodes, 14, 29, 31, 32, 33, 189, 210,
212, 218, 313, 425, 541
 
Chsetogaster, 342
 
Chaetopoda, 5, 18, 23, 41, 43, 44 , 54,
67, 209, 215, 270, 275, 307, 312, 317,
318, 319, 320, 326, 334, 33<S, 342, 346,
349, 350, 351, 364. 369. 33, 36, 408,
448, 457, 458, 521, 576,582
 
ChiXitopteridte, 333
 
Cha^tosomoidea, 371
 
Chelifer, 434, 436, 442, 446, 454
 
Chermes, 15, 429
 
Chilognatha, 113, 387, 389, 391, 393,
 
395
 
Chilopoda, 387, 392, 394
Chilostomata, 292, 297, 298, 304, 305
Chironomus, 15, 378, 401, 402, 415, 416,
 
429
 
Chiton, 254, 256, 257, 273
Chordata, 5
Chrysaora, 165
Chthonius, 436
Cicada, 395
 
Cirripedia, 459, 492, 496,503, 509, 520
Cladocera, 459, 464, 519
Clausilia, 239
Clavella, 520
Clavularia crassa, 167
Cleodora, 241
Clepsine, 73, 346, 347, 349, 351, 352,
 
353, 354
Clio, 242, 278
Clubione, 436
Clupeidae, 64
Cobitis barbatula, 378
Coccida;, 429
Coccus, 50
Ccelebogyne, 79
Coelenterata, 3, 5, 13, 18, 26, 27, 2S, 35,
 
74, 93, 94, 126, 148, 170, 178,179, 1 80,
 
181, 191, 342
 
Ccenurus cerebralis, 213, 214
Coleochaete, 1 1
 
Coleoptera, 396, 402, 409, 412, 420, 421,
^5
 
Collembola, 395, 426
Comatula, 5, 552, 553
Condracanthus, ill, 120, 520
Conochilus volvox, 22 1
Convoluta, 32
Copepoda, 109, 120, 459, 460, 487, 489,
 
493, 496, 503, 509, 519
Corallium rubrum, 168, 182
Corethra, 422, 423, 424
Crangoninoe, 476
Crnniiuhv, 311
Craniata, 5, 6, 19, 20, 54, 56, 59, 6l, 62,
 
6 4 , 74, 102
 
Crinoidea, 35, 36, 544, 550, 568, 576
Criodilus, 321, 324, 328, 341
 
 
 
INDEX.
 
 
 
Crisia, 304
Crocodilia, 63
 
Crustacea, 5, 6, 18, 51, 66, 102, 109, 120,
458, 4 6 5> 487* 5<>2, 521, 524, 537, 541
Cryptophialus, 499, 509
Crystalloides, 163
Ctenophora, 26, 93, 102, 152, 173, 175,
 
177, 178, 179, 180, 181, 182
Ctenostomata, 292, 297, 298, 304, 305
Cucullarms elegans, 46, 75, 82, 371, 376
Cucumaria, 546, 556, 574
Cumaceae, 459, 465, 486, 506
Curculio, 421
 
Cyclas, 259, 260, 261, 265
Cyclops, 376, 377, 418, 489, 503
Cyclostomata, 102, -292, 304
Cymbulia, 241, 242
 
Cymothoa, 516, 517, 519, 520,524, 528
Cynipidae, 15, 421, 428
Cyphonautes, 297, 301, 304, 306, 308
Cypridina, 500, 502
Cysticercus cellulosce, 214, 217
 
,, fasciolaris, 216
 
,, limacis, 213
 
Daphnia, 79, 464
 
Dasychone, 331, 336
 
Decapoda, 66, 248, 459, 465, 469, 504,
 
511
 
Dendroccela, 32, 33, 189, 195, 196
Dentalium, 258, 576
Desmacidon, 147
Desor, type of, 196, 197, 201, 202, 204,
 
212, 424
Diastopora, 304
Dibranchiata, 225, 253
Dicyema, 9, 131, 134, 135, 136
Dimya, 225
Diphyes, 159
Diplozoon, 11, 209, 210
Diporpa, 210
Diptera, 49, 194, 204, 396, 401,402,407,
 
409, 412, 416, 420, 429
Discina radiata, 317
Discinidse, 311
 
Discophora, 18, 42, 165, 346, 383
Distomese, 189, 205, 425
Distomum, 31
 
,, cygnoides, 209
 
,, globiparum, 207
 
,, lanceolatum, 205
Dochmius duodenale, 375
 
,, trigonocephalus, 375
Donacia, 401
Dracunculus, 376, 377
 
Echinaster fallax, 23
 
,, Sarsii, 102, 561
Echinodermata, 5, 18, 24, 35, 74, 102,
 
325, 424, 544, 573, 574, 57 6 > 5 82
Echinoidea, 35, 36, 544, 549, 565, 576
Echinorhyncus, 379, 380
 
 
 
Echinus lividus, 83, 84, 88
 
Echiurus, 44 , 357, 358
 
Ectoprocta, 297, 306
 
Edriophthalmata, 459, 465
 
Elaphocaris, 473
 
Elasmobranchii, 23, 56, 59, 61, 62, 64,
 
67, 105, 106. 107, 108, 109
Enopla, 189, 202
Entoconcha mirabilis, 237
Entomophaga, 421
 
Entoprocta, 292, 298, 300, 302, 304, 306
Epeira, 436
 
Ephemera, 395, 409, 420, 422
Ephyra, 186
 
Epibulia auranliaca, 159, 165
Erichthus, 484, 507
Errantia, 319, 336
Esperia, 147
Estheria, 463, 464
Euaxes, lol, 322, 324, 341, 346,349
Eucharis, 178
 
,, multicornis, 178
 
Eucopepoda, 459
Eucope polystyla, 23, 154
 
Eunice sanguinea, 319
 
Eupagurus prideauxii, 112, 113, 115, 511,
520
 
Euphausia, 465, 468, 504, 505, 518, 523
 
Eurostomata, 176
 
Eurylepta auriculata, 192
 
Eurynome, 483
 
Euspongia, 146, 147
 
Filaria, 377
Filaridae, 371
Firoloidea, 240
Flagellata, 7, 8
Flustrella, 301, 303
Formica, 396
Fungia, 182, 186
Fusus, 275, 280, 284, 288
 
Gammarus, 122, 518
 
,, fluviatilis, 117
,, locusta, no, 112
Ganoids, 54, 102
Gasteropoda, 39, 41, 98, 225, 226, 229,
 
230, 232, 233, 240, 258, 260, 261, 270,
 
272, 275, 279, 283, 324
Gasterosteus, 64, 210
Gastrotricha, 370
Gasterotrochce, 330, 333
Gecarcinus, 465
Geophilus, 392, 393
Gephyrea, 5, 18, 24, 44, 54, 67, 102,
 
318, 320, 325, 355, 357, 361, 364
Germogen, 134
Geryonia hastata, 156
Geryonidse, 156
Glochidia, 267, 268
Gnathobdellidas, 346, 349
Gordiacea, 94
 
 
 
588
 
 
 
INDEX.
 
 
 
Cimlioidca, 371, 374, 378
 
;nia, 168
Gorgonidce, 181
Gorgoninrc, 181
Gregarinidae, 8
Gryllotalpa, 401, 412, 413
Gunnnineiv, 147, 148
Gymnoblastic Hydroids, 184, 185
Gymnoloemata, 292
 
Gymnosomata, 225, 240, 241, 242, 270
Gyrodactylus, 210
 
Halichondria, 147
 
Ilalisarca, 22, 66, 145
 
Halistemma, 165
 
Helicidce, 238
 
Helioporidae, 182
 
Helix, 67, 229
 
Hemiptera, 395, 402, 403, 409, 420, 421
 
Hessia, 108, 492
 
Heterakis vermicularis, .374
 
Heteronereis, 343
 
Heteropoda, 71, 72, 225, 226, 231, 278
 
Hexacoralla, 152, 179, 182
 
Hippopodius gleba, 27, 159
 
Hirudinea, 74, 84
 
Hirudo, 350, 351, 352, 353, 354
 
Holometabola, 420, 422
 
Holostomum, 205
 
Holothuria, 19, 25, 35, 549, 558, 576
 
Holothuroidea, 35, 544, 553, 556
 
Homarus, 477
 
Hyaleacea, 273, 275
 
Hyaleidce, 241
 
Hydra, 21, 22, 26, 28, 29, 34, 152, 154,
 
155. 179, 183
Hydractinia, 539
Hydrocoralla, 152, 181, 185
Hydroidea, 152
Hydromedusae, 152, 179, 182, 183, 184,
 
185, 186, 187
Hydrophilus, 374, 396, 400, 401, 402,
 
404, 408, 409
Hydrozoa, 14, 19, 26, 27, 67, 102, 152,
 
155. 165. 179, 1 80, 181, 182, 539
Ilymenoptera, 396, 401, 402, 412, 420,
 
421, 425
 
Ichneumon, 396
 
Inarticulata, 311, 316
 
Incrmi
 
Infusoria, 7, 8
 
Insecta, 5, 15, 18, 19, 25, 46, 395, 396,
 
4^5, 455. 45
Intoshia gigas, 136
Isidimc, 181
Ixxlyctia, 147
Isopoda, 109, 515, 519, 521, 523, 527
 
Julus Moneletei, 387, 388, 389
Kochlorine, 499
 
 
 
Lacertilia, 64
Lacinularia, 221, 223
 
socialis, 75
Lamellibranchiata, 23, 25, 37, 39, 98,
 
225, 241, 257, 258, 259, 269, 270, 271,
 
273, 274, 288
Lepadkue, 498
 
Lepas fascicularis, 224, 493, 494, 495
Lepidoptera, 79, 396, 402, 407, 408, 412,
 
413, 415, 417, 420, 421, 423, 415, 426.
 
455
 
Leptodora, 16, 51
Leptoplana, 74, 189, 192, 193
Lernseopoda, 490, 492, 520
Leucifer, 507
 
Libellulidae, 402, 403, 409, 420
Limax, 229, 232, 239, 278, 280
Limnadia, 79, 524
Limulus, 534
Lina, 402
 
Lingulidae, 311, 316
Lithobius, 393
Lobatse, 178
 
Loligo, 242, 243, 244, 247, 253
Loricata, 507, 514
Lota, 105
 
Loxosoma, 292, 294, 296, 306, 307
Lucernaria, 185
Lumbricus, 341, 368
 
,, agricola, 321
 
,, rubellus, 324
 
trapczoides, 13, 321, 323
Lumbriconereis, 334
Lymnseus, 82, 98, 226, 227, 232, 238,
 
281
Lycosa, 436
 
Macrostomum, 32, 34
 
Macrura, 476
 
Malacobdella, 203
 
Malacodermata, 171
 
Malacostraca, 66, 459, 462, 465, 504,
 
505, 506, 511, 523
Mammalia, 56, 58, 59, 64, 66
Marsipobranchii, 59
Mastigopus, 473, 474
Medusoe, 27, 154, 157, i.^s, 16;, 164, 176,
 
178, 181, 182, 183, 184, 185, 186
Megalopa, 482, 483, 484
Melolontha, 402, 421
Membranipora, 297, 303
Mermithido;, 371
Mesotrochoe, 330
Metachoetoe, 335
Metazoa, Q, 10, 12,67, 86, 125, 135, 14^,
 
ISO, 179
 
Millepora, 152, 181
 
Mitraria, 308, 337
 
Molgula, 102
 
Mollusca, 5, 18, 24, 66, 74, 84, 99, 225,
247, 248, 251, 256, 257, 262, 271, 285,
288, 307, 325, 333, 352, 576, 582
 
 
 
INDEX.
 
 
 
589
 
 
 
Monomya, -225
Monostomum capitellum, 205
 
,, mutabile, 205, 206
 
Monotrochse, 330
Montacuta, 260, 262
Musca, 396
Muscidae, 420, 423
Myobia, 444, 445
Myrianida, 343
Myriapoda, 22, iir, 113, 387, 394, 395,
 
4i.3 458
Mynothela, 155
Myrmeleon, 396
 
Mysis, 120, 469, 472, 486, 504, 509, 525
Mytilus, 260, 261
Myxinoids, 5
Myxispongise, 145
Myzostomea, 369
 
Nais, 342
 
Nassa mutabilis, 101, 226, 227, 233, 262,
 
278, 279, 288, 3^4
Natantia, 487
Natica, 237, 283
Nauplius, 5, 16, 460, 461, 463, 465, 466,
 
469, 473, 490, 491, 493, 497
Nautilus pompilius, 253, 276
Nebaliadse, 459, 465, 486
Nematoda, 45, 46, 50, 66, 74, 75, 371,
 
373. 374> 376
Nematogens, 131
Nematoidea, 18, 84, 94, 371, 374
Nematus ventricosus, 13, 427
Nemertea, 94, 189, 196, 202, 204
Nemertines, 30, 31, 33, 93, 136, 195,
 
202, 328, 333, 424
Nephelis, 82, 346, 349, 350, 351, 352,
 
354
 
Nereis, 343
 
,, diversicolor, 319
 
,, Dumerilii, 343
Neritina, 229, 237
Neuroptera, 396, 401, 420, 421
Neuroterus ventricularis, 428
Notonecta, 395
Nototrochse, 330, 353
Nudibranchiata, 229, 241
 
Ocellata, 184
 
Octocoralla, 152, 179
 
Octopus, 248
 
Odontophora, 225, 257, 271
 
Odontosyllis, 333
 
Oedogonium, 1 1
 
Oligochseta, 42, 319, 321, 325, 330, 338,
 
346, 352
Olynthus, 144
Oniscus murarius, 107, 108, 109, 120,
 
516, 520, 528
Opercula, 31
Ophiothryx, 36, 549
Ophidia, 64
 
 
 
Ophiuroidea, 136, 544, 553, 562, 565,
 
576
 
Ophryotrochoe puerilis, 333
Opisthobranchiata, 225, 232, 237
Ornithodelphia, 109
Orthonectidae, 136
 
Orthoptera, 395, 414, 420, 421, 425, 426
Ostracoda, 459, 500, 510
Ostrea, 259, 260, 262
Oxyuridse, 46, 373, 374
Oxyurus ambigua, 374
,, vermicularis, 375
 
PcEcilopoda, 534
Paguridse, 477
Pakemon, no
Palaemonetes, 476
Pakemoninre, 476, 511, 512
Palinurus, 478, 480
 
Paludina, 66, 227, 229, 235, 270, 278,
280
 
,, costata, 229
 
,, vivipara, 226
Pandorina, n
Parasita, 489
Pedalion, 221
 
Pedicellina, 98, 292, 296, 299, 307
Pelagia, 167, 185
Penseinse, 476
Penaeus, no, 113, 465, 469, 473, 474,
 
504, 518
 
Pennatulidae, 181
Pentacrinus, 5
Pentastomida, 539, 540
Pentastomum denticulatum, 540, 54!
 
tsenoicles, 539, 540, 541
Percidae, 64
PerennichaetcE, 335
Peripatus, 5, 386, 411, 412, 413, 542
Petromyzon, 61, 63, 64, 74, 83
Phalangella, 304
Phalangidse, 436
Phallusia, 83
 
Phascolosoma, 44, 355, 356, 361
Pholcus, 436, 442
Phoronis, 315, 355, 363, 364
Phoxinus laevis, 378
Phryganea, 396, 401, 409
Phylactokemata, 292, 294, 297, 305, 306
Phyllobothrium, 218
Phyllodoce, 329
Phyllopoda, 16, 459, 461, 505
Phyllosoma, 479, 480
Phylloxera, 429
Physophoridoe, 152, 16-2, 164
Pilidium, type of, 196, 200, 201, 202, 704,
 
424
 
Pisces, 5
Piscicola, 20, 43
Pisidium, 259, 260, 262, 264
Planaria Neapolitana, 193
Planorbis, 273, 281, 325
 
 
 
590
 
 
 
INDEX.
 
 
 
Platyelminthes, 18, 20, 24, 221, 424
Platygaster, 396, 416, 417, 418, 419
Pleurohrachia, 176, 177, 238
Pneumodermon, 242, 576
Podostomata, 292
Poduridce, 401, 405
Polychaeta, 42, 319, 325, 338
Polydesmus complanatus, 387, 388
Polygordius, 319, 325, 326, 327, 328,
 
332, 357 386
Polynoe, 42, 331
Polyophthalmus, 328
Polyplacophora, 225, 254, 270, 271, 288
Polystomeas, 189, 205, 209
Polystomum, 209
 
,, integerrimum, 30, 31, 210
 
Polytrochne, 330, 333
Polyxenia leucostyla, 158
Polyxenus lagurus, 387
Polyzoa, 98, 303, 305, 306. 30 8 > 3 ! 5. 3^
Porcellana, 483
Porifera, 102, 138, 148
Porthesia, 115
Prorhyncus, 32, 34
Prosobranchiata, 225, 237, 281
Prostomum, 32, 34, 38, 196
Protozoa, 8, 9, lo, n, 86, 135, 149
Protozoaea, 471
Protula Dysteri, 342
Pseudoneuroptera, 426
Pseudoscorpionid;e, 434
Psolinus, 556, 574
Psychidae, 16
Pteraster miliaris, 561
Pteropoda, 98, 225, 226, 229, 230, 232,
 
240, 258, 270, 272, 279, 283
Pterotrachcea, 71, 229, 240
Pulex, 396
 
Pulmonata, 39, 225, 232, 238, 281, 282
I'urpura lapillus, 78
Pycnogonida, 538
Pyrosoma, 13, 53, 109
 
Rana temporaria, 210
Kaspailia, 147
Rcdia, 206, 207, 208, 209
Reniera, 147
 
Kcptilia, 56, 59, 60, 61, 62, 64, 109
Rhabditis dolichura, 82
Khabdoccela, 32, 33, iSy, ic/>
Khnbdopleura, 294, 306
Rhi/occphala, 459, 493, 499, 500
Klii/.ocrinus, 5
klii/.ostoma, 167
Rhomlx>gens, 131, 134
Khynchoncllidaj, 311
Rhyncdbddlkbe, 346
Rotifera, 5, 12, 18, 75, 76, 77, 79, 83,
102, 221, 308, 325
 
Saccocirrus, 328, 329, 332, 340
Sacculina, 500
 
 
 
Sagartia, 169, 171
 
Sagitta, 33, 74, 94, 130, 366, 367, 368
 
Salmonidrc, 64
 
Salpa, 102
 
Sarcia, 164
 
Seaphopoda, 225, 257, 270, 271
 
Schistocephalus, 2 1 1
 
Schizopoda, 459, 465, 466
 
Scolopendra, 392
 
Scorpio, 120, 43 r, 44 6, 454, 455, 457
 
Scrobicularia, 38, 39
 
Scyllarus, 477
 
Scyphistoma, 179, 185, 186
 
Sedentaria, 319, 336
 
Sepia, 20, 40, 41, 242, 243, 244, 245,
 
247> 2 49> 253
Sergestidce, 473, 507
Serpula, 319. 325, 331
Sertularia, 152, 183, 184
Silicispongia.', 147
Simulia, 401, 415
Siphonophora, 13, 77, 152, 159, 163,
 
165, 179, 1 80, 182, 185
Sipunculida, 24
Sipunculus, 44
Sirex, 396
Sitaris, 42!
 
Spathegaster baccarum, 428
Spjo, 4 2 > 33 2 > 333
Spiroptera obtusa, 376
Spirorbis Pagenstecheri, 319
 
spirillum, 319, 336
Spirula, 252
Spirulirostra, 252
Spongelia, 147
Spongida, 138, 144, 148, 149
Spongilla, 147, 150
Sporocysts, 206, 207, 208, 209
Squilla, 66, 504, 507
Stephanomia pictum, 162, 165
Stomalopoda, 459, 465, 4X4
Stomodoeum, 413
Strongylidrc, 371, 375
Strongylocentrus, 567
Strongysoloma Guerinii, 3<S7, 388, 390
Stylasterictae, 152, r8r
Styliolidic, 24!
Stylochopsis ponticus, 193
Sycandra, 93, 138, 144, 145, 147, 150
 
,, raphanus, i^S, 174
Syllis, 343
 
vivipara, 319
Sympodium coralloidcs, 168
 
Taeniatoe, 178
Tardigrada, 541
Teoenaria, 436
 
'I'clcDsti'i, IS, 25, 5^), 59, C>4. 107, io<)
I'r].)troch;i.-, 330
Tcndra, 300
'I '(.'nth reds, 396
Tcrcbdla concliilcga, 332, 333, 337
 
 
 
INDEX.
 
 
 
591
 
 
 
Terebella nebulosa, 332, 333
Terebratula, 311, 315
Terebratulina, 311, 315, 316
 
,, septentrionalis, 315, 316
 
Teredo, larva of, 262
Tergipes, 232, 238
 
,, Edwardsii, 238
,, lacinulatus, 238
Tethya, 147
Tetrabranchiata, 225
Tetranychus telarius, 116
Tetrastemma varicolor, 203
Thalassema, 44, 355, 357
Thalassinidae, 477
Thallophytes, n
Thecidium, 311, 312, 315, 316
Thecosomata, 225
Thoracica, 459, 493, 499, 500
Thysanozoon, 192, 193
Thysanura, 395, 408, 425, 458
Tichogonia, 39
Tipula, 396
Tipulidae, 420, 421
Toenia cosnurus, 214
 
,, echinococcus, 215, 217
 
solium, 217
Tornaria, 579, 581
Toxopneustes, 22, 24, 35, 85, 88, 89
Tracheata, 385, 426, 432, 44 8, 455, 457,
 
458, 538, 54i
 
Trachymedusae, 152, 156, 179, 185
Trematodes, 14, 16, 29, 30, 31, 32, 33,
 
46, 94, 189, 205, 208, 210, 212, 216
 
 
 
Trichina, 377, 378
 
Trichinidse, 371
 
Trichocepha'lus affinis, 374
 
Trochosphsera aequatorialis, 221
 
TubiporidcE, 182
 
Tubularia, 34, 38, 152, 154, 158
 
Tubularidse, 29, 179, 183
 
Tunicata, 5, I 4 , 53
 
Turbellaria, 5, 30, 31, 33, 74, 98, 102,
 
136, 179, 189, 193, 333
Tyroglyphus, 445
 
Unio, 37, 38, 39, 100, 101, 259, 260,265,
266, 445
 
Vaginulus luzonicus, 229
 
Vermes, 5, 74, 102, 223, 324, 352
 
Verongia rosea, 146
 
Vertebrata, 14, 18, 19, 24, 59, 64, 83,
 
272, 349. 397' 4^6
Vesiculata, 184
Vitrina, 229
Vorticella, 8, 9, 10
 
Wilsia, 164
Xiphoteuthis, 252
 
Zoantharia, 152, 168, 169
Zooea, 465, 468, 471, 474, 482, 483, 484,
486, 504
 
 
 
BIBLIOGRAPHY.
 
 
 
THE OVUM.
 
General Works.
 
(1) } Ed. van Beneden. "Recherches sur la composition et la signification de
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THE OVUM OF CCELENTERATA.
 
(7) Ed. van Beneden. "De la distinction originelle d. testicule et de
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(8) R. and O. Hertwig. Der Organismus d. Medusen. Jena, 1878.
 
(9) N. Kleinenberg. Hydra. Leipzig, 1872.
 
THE OVUM OF PLATYELMINTHES.
 
(10) P. Hallez. Contributions a fHistoire naturelle des Turbellarih. Lille,
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(11) S. MaxSchultze. Beitrdge z. Naturgeschichte d. Turbellarien. Greifswald, 1851.
 
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[Vide also Ed. van Beneden (No. i).]
 
THE OVUM OF ECHINODERMATA.
 
(15) C. K. Hoffmann. " Zur Anatomic d. Echiniden u. Spatangen." Niederllindisch. Archiv f. Zoologie, Vol. I. 1871.
 
(16) C. K. Hoffmann. " Zur Anatomic d. Asteriden. Niederldndisch. Ardiiv
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[Vide also Ludwig (No. 4), etc.]
 
1 A very complete and critical account of the literature is contained in this paper.
B. II. a
 
 
 
BIBLIOGRAPHY.
 
 
 
THE OVUM OF MOLLUSC A.
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Wiss. men, Vol. LXXI. 1875.
 
(24) Th. von Hassling. " Einige Bemerkungen, etc." Zeit. f. wiss. ZooL,
Bd. v. 1854.
 
(25) H. von Jhering. "Zur Kenntniss d. Eibildung bei d. Muscheln." Zeit.
f. wiss. ZooL, Vol. xxix. 1877.
 
(26) Keber. De Introihi Spermatozoorum in ovula, etc. Konigsberg, 1853.
 
(27) Fr. Leydig. " Kleinere Mittheilung etc." Miiller's Archiv, 1854.
 
Gasteropoda.
 
(28) C. Semper. "Beitrage z. Anat. u. Physiol. d. Pulmonaten." Zeit. f.
wiss. ZooL, Vol. vni. 1857.
 
(29) H. Eisig. " Beitrage z. Anat. u. Entwick. d. Pulmonaten." Zeit.f. wiss.
ZooL, Vol. xix. 1869.
 
(30) Fr. Leydig. " Ueb. Paludina vivipara." Zeit.f. wiss. ZooL, Vol. u. 1850.
 
Cephalopoda.
 
(31) Al. Kolliker. Entwicklungsgeschichte d. Cephalopoden. Zurich, 1844.
 
(32) E. R. Lankester. "On the Developmental History of the Mollusca."
Phil. Trans., 1875.
 
THE OVUM OF THE CHJETOPODA.
 
(33) Ed. Claparede. " Les Annelides Chaetopodes d. Golfe de Naples."
Mem.d. 1. Soctit. phys. eld 1 hist. nat. de Geneve, 1868 9 and 1870.
 
(34) E. Ehlers. Die Borstcnwiirmer nach system, und anat. Untersuchungen.
Leipzig, 186468.
 
(35) E. Selenka. " Das Gefass-System d. Aphrodite aculeata." Niedcrldndisches Archiv f. ZooL, Vol. n. 1873.
 
THE OVUM OF DISCOPHORA.
 
(36) H. Dorner. " Ueber d. Gattung Branchiobdella." Zeit.f. wiss. ZooL,
Vol. xv. 1865.
 
(37) R. Leuckart. Die menschlichen Parasiten.
 
(38) Fr. Leydig. "Zur Anatomie v. Piscicola eeometrica, etc." Zeit. f. wiss.
ZooL, Vol. I. 1849.
 
(30) C. O. Whitman. "Embryology of Clepsine." Quart. 7. of Alter.
Sci., Vol. xvin. 1878.
 
THE OVUM OF GEPHYREA.
 
(40) Keferstein u. Ehlers. Zoologische Beitrage. Leipzig, 1861.
 
(41) C. Semper. Holothurien, 1868, p. 145.
 
(42) J. W. Spengel. " Beitrage z. Kenntniss d Gephyreen." Beitriigc a. d.
zool. Stationz. Neapcl, Vol. I. 1879.
 
(43) J. W. Spengel. " Anatomische Mittheilungen lib. Gephyreen." Tagcbl.
d. Naturf. Vers. Munchen, 1877.
 
THE OVUM OF NEMATODA.
 
(44) Ed. Claparede. De la formation ct de la fccondaiiou dcs- n-uf.\ chcz Ics
I'crs Ntmatodcs. (ienevc, 1859.
 
(J- r )) K. I. (.-nek art. Hif nirnsf/i lichen Paras! ten.
 
 
 
BIBLIOGRAPHY. jjj
 
 
 
d.Nematoden."
 
^' Nels0n * " On the reproduction of Ascaris mystax, etc." Phil.
(48) A.Schneider. Monographie d.' Nematoden. Berlin, 1866.
THE OVUM OF INSECT A.
 
 
 
Sm ' T? r u n d V Ueb ,?'* a5 Ei u ' seine Bildungsstdtte. Leipzig, 1 878.
(50) T. H. Huxley. " On the agamic reproduction and morphology of Aphis.
Ltnnean Trans., Vol. xxn. 1858. Vide also Manual of Invertebrate* Animals, 1877.
 
1 * ^ ^ ^ *
 
 
 
(51)
bei den *,++,*
 
/-a\ ? r ',k ey< MS' Der Eierstock u. die Samentasche d. Insecten. Dresden, 1866.
tSl ~ ub . bock - " The ov a and pseudova of Insects." Phil. Trans. 1850.
(o4) Stem. Die weiblichen Geschlcchtsorgane d. Ktifer. Berlin, 1847.
[Conf. also Glaus, Landois, Weismann, Ludwig (No. 4).]
 
THE OVUM OF ARANEINA.
 
(55) Victor Cams. " Ueb. d. Entwick. d. Spinneneies." Zeit. f. wiss. Zool. t
Vol. ii. 1850.
 
(56) v. Wittich. "Die Entstehung d. Arachnideneies im Eierstock, etc."
Miiller s Archiv, 1849.
 
[Conf. Leydig, Balbiani, Ludwig (No. 4), etc.]
 
THE OVUM OF CRUSTACEA.
 
(57) Aug. Weismann. "Ueb. d. Bildung von Wintereiern bei Leptodora
hyalina." Zeit.f. wiss.ZooL, Vol. xxvn. 1876.
 
[For general literature vide Ludwig, No. 4, and Ed. van Beneden, No. i.]
 
THE OVUM OF CHORD ATA.
 
Urochorda (Tunicata).
 
(58) A. Kowalevsky. " Weitere Studien ii. d. Entwicklung d. Ascidien."
Archiv f. micr. Anat., Vol. VII. 1871.
 
(59) A. Kowalevsky. "Ueber Entwicklungsgeschichte d. Pyrosoma."
Arch.f. micr. Anat., Vol. xi. 1875.
 
(60) Kupffer. " Stammverwandtschaft zwischen Ascidien u. Wirbelthieren."
Arch. f. micr. Anat., Vol. VI. 1870.
 
(61) Giard. " Etudes critiques des travaux, etc. " Archives Zool. experiment.,
Vol. I. 1872.
 
(62) C. Semper. " Ueber die Entstehung, etc." Arbeiten a. d. zool.-zoot.
Institut Wiirzburg, Bd. II. 1875.
 
Cephalochorda.
 
(63) P. Langerhans. "Z. Anatomic d. Amphioxus lanceolatus," pp. 330 3.
Archiv f. mikr. Anat., Vol. xil. 1876.
 
Craniata.
 
(64) F. M. Balfour. "On the structure and development of the Vertebrate
Ovary." Quart. J. of Micr. Science, Vol. xvm. 1878.
 
(65) Th. Eimer. " Untersuchungen ii. d. Eier d. Reptilien." Arckiv f.
mikr. Anat., Vol. vni. 1872.
 
(66) Pfliiger. Die Eierstbcke d. Sdugethiere u. d. Menschen. Leipzig, 1863.
 
(67) J. Foulis. " On the development of the ova and structure of the ovary in
Man and other Mammalia." Quart. J. of Micr. Science, Vol. XVI. 1876.
 
(68) J. Foulis. " The development of the ova, etc." Journal of Anat. and
Phys., Vol. xni. 18789.
 
a 2
 
 
 
IV BIBLIOGRAPHY.
 
 
 
(69) C. Gegenbaur. " Ueb. d. Bau u. d. Entwicklung d. Wirbelthiereier mit
partieller Dottertheilung." Muller's Archiv, 1861.
 
(70) Alex. Gotte. Entwicklungsgeschichte d. Unke. Leipzig, 1875.
 
(71) W. His. Untersuchungen iib. d. Ei u. d. Eientwicklung bei Knochenfischcn.
Leipzig, 1873.
 
(72) A. Kolliker. Entwicklungsgeschichte d. Menschen u. hoherer Thicre,
Leipzig, 1878.
 
(73) J. Miiller. " Ueber d. zahlreichen Porenkanale in d. Eikapsel d. Fische."
Muller's Archiv, 1854.
 
(74) W. H. Ransom. " On the impregnation of the ovum in the Stickleback."
Pro. K. Society, Vol. vn. 1854.
 
(75) C. Semper. " Das Urogenitalsystem d. Plagiostomen etc." Arbeiten a.
d. zool.-zoot. Instit. Wiirzburg, Vol. II. 1875.
 
[Cf. Ludwig, No. 4, Ed. van Beneden, No. i, Waldeyer, No. 6, etc.]
 
 
 
MATURATION AND IMPREGNATION OF THE OVUM.
 
(76) Auerbach. Organologische Studien, Heft 2. Breslau, 1874.
 
(77) Bambeke. " Recherches s. Embryologie des Batraciens." Bull, de
royale de Belgique, 2me ser., T. LXI. 1876.
 
(78) E. van Beneden. " La Maturation de 1'CEufdes Mammiferes." Bull,
de fAcad. royale de Belgique, 2me ser., T. XL. No. 12, 1875.
 
(79) Id em. " Contributions a 1'Histoire de la Vesicule Germinative, &c." Bull,
de fAcad. royale de Belgique, sme ser., T. XLI. No. i, 1876.
 
(80) O. Biitschli. Eizelle, Zelltheilung, und Conjugation der Infusorien.
Frankfurt, 1876.
 
(81) F. M. Balfour. " On the Phenomena accompanying the Maturation and
Impregnation of the Ovum." Quart. J. of Micros. Science, Vol. xvm. 1878.
 
(82) Calberla. " Befruchtungsvorgang beim Ei von Petromyzon Planeri.*'
Zeit. f. iviss. Zool., Vol. xxx.
 
(83) W. Flemming. "Studien in d. Entwickelungsgeschichte der Najaden."
Sitz. d. k. Akad. Wiett, B. LXXI. 1875.
 
(84) H. Fol. "Die erste Entwickelung des Geryonideneies. " Jenaische
Zeitschrift, Vol. vn. 1873.
 
(85) Idem. " Sur le Developpement des Pte"ropodes." Archives de Zoologic
Experimental et Gtnerale, Vol. iv. and v. 1875 6.
 
(86) Idem. " Sur le Commencement de 1'Henog^nie." Archives des Sciences
Physiques et Naturelles. Geneve, 1877.
 
(87) Idem. Recherches s. I. Ftcondation etl. comrnen. d. rHcnogcnic. Geneve, 1879.
 
(88) R. Greeff. " Ueb. d. Bau u. d. Entwickelung d. Echinodermen." Sitzun.
der Gesellschaft z. Befonlerung d. gesammten Naturwiss. z. Marburg, No. 5, 1876.
 
(89) Oscar Hertwig. " Beit. z. Kenntniss d. Bildung, &c., d. thier. Eies."
Morphologisches Jahrbuch, Vol. I. 1876.
 
(90) Idem. Ibid. Morphologisches Jahrlntch, Vol. ill. Heft i, 1877.
 
(91) Idem. " Weitere Beitrage, &c." Morphologisches Jahrbuch, Vol. in. 1877.
Heft 3.
 
(92) Idem. "Beit. z. Kenntniss, &c." Morphologisches Jahrbuch, Vol. iv.
Heft i and 2. 1878.
 
(93) N. Kleinenberg. Hydra. Leipzig, 1872.
 
(94) C. Kupffer u. B. Benecke. Der Vorgang d. llcfnichtinig am Eie d.
Neunaugen. Konigsberg, 1878.
 
(95) J. Oellacher. "Beitrage zur Geschichte des Keimblaschens im Wirbelthicreie." Archiv f. micr. Anat., Bd. VIII. 1872.
 
(%) W. Salensky. " Befruchtung u. P^urchung d. Sterlets-Eies." Zoologischer Anzeigcr, No. 11, 1878.
 
(97) E. Selenka. Befruchtung des Eies von Toxopncustcs variegatus. Leipzig,
1878.
 
fl Strasburger. Ucber Zclllnldu n- n. /.clltln ////;/;. Ji-na, 1876.
 
Idem. Utber Befrvehtung u. Zdlthdhing. Jena, 1X78.
 
(HiO) C. (). \V hi tin.in. "Tlic- Kniliryology of Clepsine." Quart. J. of A/i<r.
Science, Vol. xvm. 1878.
 
 
 
BIBLIOGRAPHY.
 
 
 
DIVISION OF NUCLEUS.
 
(101) W. Flamming. "Beitrage z. Kenntniss d. Xclle u. ihrcr Lcbun.scrschcinungen." Archiv f. mikr. Anat., Vol. xvi. 1878.
 
(102) E. Klein. "Observations on the glandular epithelium and division of
nuclei in the skin of the Newt." Quart, y. of Micr. Science, VoL XIX. 1879.
 
(103) Peremeschko. "Ueber d. Theilung d. thierischen Zellen." Archiv f.
mikr. Anat., Vol. xvi. 1878.
 
(104) E. Strasburger. "Ueber ein z. Demonstration geeignetes ZclltheilungsObject." Sitz. d. Jenaischen Gesell.f. Med. u. Naturwiss., July 18, 1879.
 
SEGMENTATION.
 
(105) E. Haeckel. "Die Gastrula u. Eifurchung." Jenaische Ztitschrift, Vol.
ix. 1877.
 
(106) Fr. Leydig. "Die Dotterfurchung nach ihrem Vorkommen in d. Thierwelt u. n. ihrer Bedeutung." Oken. /sis, 1848.
 
GENERAL WORKS ON EMBRYOLOGY.
 
(107) K. E. von Baer. " Ueb. Entwicklungsgeschichte d. Thiere." Konigsberg, 182837.
 
(108) C. Glaus. Grundziige d. Zoologie. Marburg und Leipzig, 1879.
 
(109) C. Gegenbaur. Grundriss d. vergleichenden Anatomie. Leipzig, 1878.
Vide also Translation. Elements of Comparative Anatomy. Macmillan and Co.,
1878.
 
(110) E. Haeckel. Studien z. Gastrcea-Theorie. Jena, 1877, and also Jenaische Zeitschrift, Vols. vni. and ix.
 
(111) E. Haeckel. Schopfungsgeschichte. Leipzig. Vide also Translation.
The History of Creation. King and Co., London, 1876.
 
(112) E. Haeckel. Anthropogenie. Leipzig. Vide also Translation. Anthropogeny (Translation). Kegan Paul and Co., London, 1878.
 
(113) Th. H.Huxley. The Anatomy of Invertebrated Animals. Churchill,
1877.
 
(114) E. R. Lankester. "Notes on Embryology and Classification." Quart.
J. of Micr. Science, Vol. xvi I. 1877.
 
(115) A. S. P. Packard. Life Histories of Animals, including Man, or Outlines
of Comparative Embryology. Holt and Co., New York, 1876.
 
(116) H. Rathke. Abhandlungen z. Bildung- und Entwicklungsgesch. d. Menschen u. d. Thiere. Leipzig, 1833.
 
DICYEMID.E.
 
(117) E van Beneden. "Recherches sur les Dicyemides." Bull. d. FAcadtmie roy. de Belgique, f ser. T. XLI. No. 6 and T. XLII. No. 7, 1876. Vide this
paper for a full account of the literature.
 
(118) A. K 611 ike r. Ueber Dicyema paradoxum den Schmarotzer der Venenanhiinge der Cephalopoden. ,
 
(119) Aug. Krohn. "Ueb. d. Vorkommen von Entozoen, etc. Fronep
 
Notizen, vn. 1839.
 
ORTHONECTID^E.
 
(120) A If. Giard. "Les Orthonectida classe nouv. d. Phylum des Vers."
journal de tAnat. et de la Physiol., Vol. XV. 1879.
 
(121) El. Metschnikoff. "Zur Naturgeschichte d. OrthonecUdae." Zoologi
scher Anzeiger, No. 40 43 l8 79
PORIFERA.
'(122) C Barrois. " Embryologie de quelques eponges de la Manche. " An
""$) & &ZS^^'<t*>* SP"6es." A~* ^ M g . cf
Nat. Hist., 4th series, Vol. xiv. 1874.
 
 
 
 
 
 
vi BIBLIOGRAPHY.
 
 
 
(124) Ganin 1 . " Zur Entwicklung d. Spongilla fluviatilis." Zoologischer Anzeigtr, Vol. i. No. 9, 1878.
 
(125) Robert Grant. "Observations and Experiments on the Structure and
Functions of the Sponge." Edinburgh Phil. jf., Vol. xm. and XIV., 1825, 1816.
 
(126) E. Haeckel. Die Kalkschwamme, 1872.
 
(127) E. Haeckel. Studien zur Gastraa- Theorie. Jena, 1877.
 
(128) C. Keller. Unterstichungen iiber Anatomic und Entwicklungsgeschichte
einiger Spongien. Basel, 1876.
 
(129) C. Keller. "Studien lib. Organisation u. Entwick. d. Chalineen." Zeit.
f. wiss. Zoo/., Bd. xxvin. 1879.
 
(130) LieberkUhn. "Beitr. z. Entwick. d. Spongillen." Muller's Archiv,
1856.
 
(131) LieberkUhn. "Neue Beitrage zur Anatomie der Spongien." Miiller's
Archiv, 1859.
 
(132) El. Metschnikoff. " Zur Entwicklungsgeschichte der Kalkschwamme. "
Zeit.f. wiss. Zool., Bd. xxiv. 1874.
 
(133) El. Metschnikoff. "Beitrage zur Morphologic der Spongien." Zeit.
f. wiss. Zool., Bd. xxvii. 1876.
 
(134) El. Metschnikoff. " Spongeologische Studien." Zeit. f. wiss. Zool.,
Bd. xxxn. 1879.
 
(135) Miklucho Maklay. "Beitrage zur Kenntniss der Spongien." Jenaische
Zeitschrift, Bd. iv. 1868.
 
(136) O. Schmidt. "Zur Orientirung iiber die Entwicklung der Schwamme."
Zeit.f. wiss. Zool., Bd. xxv. 1875.
 
(137) O. Schmidt. "Nochmals die Gastrula der Kalkschwamme." Archiv
fur mikrosk. Anat., Bd. XII. 1876.
 
(138) O. Schmidt. "Das Larvenstadium von Ascetta primordialis und Asc.
clathrus." Archiv fur mikrosk. Anatomie, Bd. xiv. 1877.
 
(139) F. E. Schulze. "Ueber den Bau und die Entwicklung von Sycandra
raphanus." Zeit.f. wiss. Zool., Bd. xxv. 1875.
 
(140) F. E. Schulze. "Zur Entwicklungsgeschichte von Sycandra." Zeit. f.
wiss. Zool., Bd. XXVII. 1876.
 
(141) F. E. S chulze. " Untersuchung Ub. d. Bau, etc. Die Gattung Halisarca."
Zeit.f. wiss. Zoo/., Bd. xxvin. 1877.
 
(142) F. E. Schulze. "Untersuchungen iib. d. Bau, etc. Die Metamorphose
von Sycandra raphanus." Zeit.f. wiss. Zool., Bd. xxxi. 1878.
 
(143) F. E. Schulze. "Untersuchungen u. d. Bau, etc. Die Familie Aplysinidae." Zeit.f. wiss. Zool., Bd. xxx. 1878.
 
(144) F. E. Schulze. "Untersuchungen u. d. Bau, etc. Die Gattung Spongelia." Zeit.f. wiss. Zool., Bd. xxxn. 1878.
 
CCELENTERATA.
General.
 
(145) Alex. Agassi z. Illustrated Catalogue of the Museum of Comparative
Anatomy at Harvard College, No. II. American Acalephac. Cambridge, U. S., 1865.
 
(140) O. and R. Hertwig. Der Organismus d. Medusa: u, seine Stellung z.
Keimblattertheorie. Jena, 1878.
 
(147) A. Kowalevsky. "Untersuchungen lib. d. Entwicklung d. Coelenteraten." Nachrichten d. kaiser. Gcsell. d. Freunde d. Nattirerkenntniss d. Antliropologie u. Ethnographie. Moskau, 1873. (Russian). For abstract vide Jahresberichtc
d. Anat. u. Phys. (Hoffman u. Schwalbe), 1873.
 
Hydrozoa.
 
(148) L. A gas si z. Contributions to the Natural History of the United States of
America. Boston, 1862. Vol. IV.
 
(149) G. J. Allman. A Monograph of the Gymnoblastic or Tubularian Hydrotds. Ray Society, 1871-2.
 
1 There is a Russian paper by the same author, containing a full account, with
clear illustrations, of his observations.
 
 
 
BIBLIOGRAPHY, vii
 
 
 
(150) G. J. All man. "On the structure and development of Myriothela." Phil.
Trans., Vol. CLXV. p. 2.
 
(Iff), P - J- van Beneden. "Mem. sur les Campanulaires de la Cote d'Ostende
consideres sous le rapport physiologique, embryogenique, et zoologique." Nouv. Mini.
de PAcad. de Brux., Tom. xvn. 1844.
 
(^ 2 ) p - J- van Beneden. "Recherches sur 1'Embryogenie des Tubulaires et
1 histoire naturelle des differents genres de cette famille qui habitent la Cote d'Ostende."
Nouv. Mem. de P Acad. de Brux., Tom. xvii. 1844.
 
(153) C. Claus. "Polypen u. Quallen d. Adria." Denk. d. math.-naturwiss.
Classe d. k. k. Akad. d. Wiss. Wien, Vol. xxxvin. 1877.
 
(154) J. G. Dal yell. Rare and Remarkable Animals of Scotland. London,
1847.
 
(* 55 ) , H - Fo1 - " Die er ste Entwicklung d. Geryonideneies." J 'enaische Zeit
schrift, Vol. vn. 1873.
 
(156) Carl Gegenbaur. Zur Lehre vom Generationswechsel und der Fortpfianzung bei Medusen und Polypen. Wiirzburg, 1854.
 
(157) Thomas Hincks. "On the development of the Hydroid Polypes, Clavatella and Stauridia ; with remarks on the relation between the Polype and the Medusoid, and between the Polype and the Medusa." Brit. Assoc. Rep., 1861.
 
(158) E. Haeckel. Zur Entwicklungsgeschichte d. Siphonophoren. Utrecht,
1869.
 
(159) Th. H. Huxley. Oceanic Hydrozoa. Ray Society, 1858.
 
(160) Geo. Johnston. A History of British Zoophytes. Edin. 1838. 2nd
Edition, 1847.
 
(161) N. Kleinenberg. Hydra, eine anatomisch-entwicklungsgeschichtliche Untersuchung. Leipzig, 1872.
 
(162) El. Metschnikoff. "Ueber die Entwicklung einiger Ccelenteraten."
Bull, de FAcad. de St Petersbourg, XV. 1870.
 
(163) El. Metschnikoff. "Studien liber Entwicklungsgeschichte d. Medusen
u. Siphonophoren." Zeit.f. wiss. ZooL, Bd. xxiv. 1874.
 
(164) H. N. Moseley. "On the structure of the Sty lasteridse." Phil. Trans.,
 
(165) F. E. Schulze. Ueber den Bau und die Entwicklung von Cordylophora
lacustris. Leipzig, 1871.
 
Actinozoa.
 
(166) Al. Agassiz. "Arachnitis (Edwarsia) brachiolata." Proc. Boston Nat.
Hist. Society, 1860.
 
(167) Koch. "Das Skelet d. Alcyonarien." Morpholog. Jahrbuch, Bd. iv.
1878.
 
(168) A. Kowalevsky. "Z. Entwicklung d. Alcyoniden, Sympodium coralloides und Clavularia crassa." Zoologischer Anzeiger, No. 38, 1879.
 
(169) H. Lacaze Duthiers. Histoire nat.du Cor ail. Paris, 1864.
 
(170) H. Lacaze Duthiers. " Developpement des Coralliaires." Archives
de Zoologie experimental et generate, Vol. I. 1872 and Vol. u. 1873.
 
(171) C. Semper. " Ueber Generationswechsel bei Steinkorallen etc." Zeit. f.
wiss. ZooL, Bd. xxii. 1872.
 
Ctenophora.
 
(172) Alex. Agassiz. "Embryology of the Ctenophorae." Mem. of the Anur.
Acad. of Arts and Sciences, Vol. X. No. 1 1 1. 1874.
 
(173) G. J. All man. "Contributions to our knowledge of the structure and development of the Beroidse." Proc. Roy. Soc. Edinburgh, Vol. IV. 1862.
 
(174) C. Chun. "Das Nervensystem u. die Musculatur d. Rippenquallen."
Abhand. d. Senkenberg. Gesellsch., B. XI. 1879.
 
(175) C. Claus. "Bemerkungen u. Ctenophoren u. Medusen." Zeit. f. wiss.
ZooL, xiv. 1864.
 
(176) H. Fol. Ein Beitrag z. Anat. u. Entwickl. einiger Rippenquallen. 1869.
 
(177) C. Gegenbaur. "Studien u. Organis. u. System d. Ctenophoren."
Archiv f. Naturgesch., xxii. 1856.
 
(178) A. Kowalevsky. " Entwicklungsgeschichte d. Rippenquallen. " Mtm.
Acad. St Petersbourg, vii. serie, Tom. x. No. 4. 1866.
 
 
 
Vlii BIBLIOGRAPHY.
 
 
 
(179) J. Price. "Embryology of Ciliogrades." Proceed, of British Assoc.,
1846.
 
(180) C. Semper. "Entwicklung d. Eucharis multicornis." Zeit. f. wtss.
Zool., Vol. IX. 1858.
 
PLATYELMINTHES.
Turbellaria.
 
(181) Alex. Agassiz. "On the young stages of a few Annelids" (Planaria angitlata). Annals Lyceum Nat. Hist, of Neiv York, Vol. vin. 1866.
 
(182) Dalyell. "Powers of the Creator."
 
(183) C. Girard. "Embryonic development of Planocera elliptica." J our. of
Acad. of Nat. Set., Philadelphia. New Series, Vol. II. 1854.
 
(184) Alex. Gotte. "Zur Entwicklungsgeschichte d. Seeplanarien." Zoologischer Anzeiger, No. 4, 1878.
 
(185) P. Halle z. Contributions a Thistoire naturelle des Turbellarits. Thesis a
la facult^ des Sciences p. le grade d. Docteur es-sciences naturelles. Lille, 1879.
 
(186) Knappert. "Bijdragen tot de Ontwikkelings-Geschiedenis der Zoetwater-Planarien." Provinciaal Ulrechtsch Genootschap van Kunsten en Wetenschappen. Utrecht, 1865.
 
(187) W. Keferstein. " Beitrage z. Anat. u. Entwick. ein. Seeplanarien von
St. Malo." Abh. d. konig. Gesell. d. Wiss. zu Gottingcn. Bd. XI v. 1868.
 
(188) El. Metschnikoff. " Untersuchungen lib. d. Entwicklung d. Planarien."
Notizen d. neurussischen Gesellschaft d. Naturforscher. Odessa, Bd. V. 1877. Vide
Hoffman and Schwalbe's Bericht for 1878.
 
(189) H. N. Moseley. "On Stylochus pelagicus and a new species of pelagic
Planarian, with notes on other pelagic species, on the larval forms of Thysanozoon,
etc." Quart. Journ. of Micr. Science, Vol. xvn. 1877.
 
(190) J. Miiller. "Ueber eine eigenthiimliche Wurmlarva a. d. Classe d. Turbellarien, etc." Miiller's Archiv f. Anat. u. Phys. 1850.
 
(191) J. Miiller. "Ueber verschiedene Formen von Seethieren." Miiller's
Archiv f. Anat. und Phys. 1854.
 
Nemertea.
 
(192) J. Barrois. " L'Embryologie des Nemertes." An. Sci. Nat., Vol. VI.
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(193) O. BUtschli. Archiv f. Naturgeschichte, 1873.
 
(194) A. Krohn. "Ueb. Pilidium u. Actinotrocha." Miiller's Archiv, 1 858.
 
(195) E. Desor. "Embryology of Nemertes." Proceedings of the Boston Nat.
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(196) G. Dieck. "Entwicklungsgeschichte d. Nemertinen." Jenaische Zeitschrift, Vol. vin. 1874.
 
(197) C. Gegenbaur. "Bemerkungen lib. Pilidium gyrans, etc." Zeitschrift
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(198) C. K. Hoffman. "Entwicklungsgeschichte von Tetrastemma tricolor."
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(199) C. K. Hoffman. "Zur Anatomie und Ontogenie von Malacobdella."
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(200) W. C. M c Intosh. British Annelids. The Nemerteans. Ray Society,
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(201) Leuckart u. Pagenstecher. "Untersuchungen lib. niedere Seethiere."
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(202) E. Metschnikoff. "Studien lib. die Entwicklung d. Echinodermen u.
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Trematoda.
 
(203) T. S. Cobbold. Kntozoa. Groombridge and Son, 1864.
 
(204) T. S. Cobbold. Parasites; a Treatise on the Entozoa, etc. Churchill,
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BIBLIOGRAPHY. ix
 
 
 
206) R. Leuckart. Die menschlichen Parasilen, Vol. I. 1863, p. 485 ct seq.
 
207) H. A. Pagenstecher. Trematodtn u. Trematodenlarven. Heidelberg,
 
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(208) C. Th. von Siebold. Lehrbuch d. vergleich. Anat. wirbelloser Thicre.
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( 209 ) J- J- S. Steenstrup. Generationswechsel. 1842.
 
(210) R. v. Willemoes-Suhm. "Zur Naturgeschichte d. Polystomuiu intcgerrimum, etc." Zeit.f. wiss. Zool., Vol. xxn. 1872.
 
(211) R. v. Willemoes-Suhm. ''Helminthologische Notizcn III." Zeit. f.
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(212) G. R. Wagener. Beitrdge zur Entwicklungsgeschichte d. Eingeweidewiirmer. Haarlem, 1855.
 
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(214) G. R. Wagener. "Ueb. Gyrodactylus elegans." Archiv f. Anat. u.
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(215) E. Zeller. " Untersuchungen ub. d. Entwicklung d. Diplozoon paradoxum." Zeit.f. wiss. Zool., Vol. xxn. 1872.
 
(216) E. Zeller. "Untersuchungen u. d. Entwick. u. Bau d. Polystomum integerrimum." Zeit.f. wiss. Zool., Vol. xxn. 1872.
 
(217) E. Zeller. "Weitere Beitrage z. Kenntniss d. Polystomen." Zeit.f.
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Cestoda.
 
(218) Ed. van Beneden. "Recherches sur la composition et la signification
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(219) P. J. van Beneden. "Les vers Cestoi'des consideres sous le rapport
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(220) T. S. Cobbold. Entozoa. Groombridge and Son, 1864.
 
(221) T. S. Cobbold. Parasites; a treatise on the Entozoa, etc. Churchill,
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(222) Th. H. Huxley. "On the Anatomy and Development of Echinococcus
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(223) J. Knoch. "Die Naturgesch. d. breiten Bandwiirmer." Mem. Acad.
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(224) F. Kiichenmeister. "Ueber d. Umwandlung d. Finnen Cysticerci in
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(225) F. Kiichenmeister. "Experimente iib. d. Entstehung d. Cestoden.
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(226) R. Leuckart. Die menschlichen Parasiten, Vol. I. Leipzig, 1863. Vide
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(227) R. Leuckart. "Archigetes Sieboldii, eine geschlechtsreife Cestodenamme." Zeit.f. wiss. Zool., Vol. xxx. Supplement, 1878.
 
(228) El. Metschnikoff. "Observations sur le developpement de quelques
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(229) 'w. Salensky. "Ueb. d. Bau u. d. Entwicklungsgeschichte d. Amphilina." Zeit.f. wiss. Zool., Vol. xxiv. 1874.
 
(230) Von Siebold. Burdach's Physiologie.
 
(231) R. von Willemoes-Suhm. "Helminthologische Notizen." Zfit. /.
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ROTIFERA.
 
(232) F. Cohn. "Ueb. d. Fortpflanzung von Raderthiere." Zeit.f. wiss.
 
^(233) F. Cohn. "Bemerkungen u. Raderthiere." Zeit.f. wiss. Zool., Vol. IX.
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(234) T. H. Huxley. "Lacinularia socialis." Trans, of the Microscopical
 
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BIBLIOGRAPHY.
 
 
 
(235) Fr. Leyclig. " Ueb. d. Bau u. d. systematische Stelluny; d. Radcrthiere."
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(236) W. Salensky. "Beit. z. Entwick. von Brachionus urceolaris." Zeit. /.
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(237) C. Semper. " Zoologische Aphorismen. Trochosphuera axjuatorialis."
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MOLLUSCA.
 
General.
 
(238) T. H. Huxley. "On the Morphol. of the Cephal. Mollusca." Phil.
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(239) E. R. Lankester. "On the developmental history of the Mollusca."
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(240) H. G. Bronn and W. Keferstein. Die Klasscn u. Ordnungcn d.
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Gasteropoda and Pteropoda.
 
(241) J. Alder and A. Hancock. "Devel. of Nudibr." Ann. and Magaz.
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(242) N. Bobretzky. "Studien iiber die embryonale Entwicklung d. Gasteropoden." Archivf. micr. Anat., Vol. xin.
 
(243) W. K. Brooks. "Preliminary Observations on the Development of
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(244) O. Biitschli. " Entwicklungsgeschichtliche Beitrage (Paludina vivipara)."
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(245) W. Carpenter. "On the devel. of the embr. of Purpura lapillus."
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(246) W. Carpenter. "On the devel. of the Purpura." Ann. and Mag. of
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(247) E. Claparede. "Anatomic u. Entwickl. der Neritina fluviatilis."
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(248) H. Eisig. "Beitr. z. Anat. u. Entwickl. der Geschlechtsorg. von Lymnieus." Zeitschr. f. wiss. Zool., Vol. xix. 1869.
 
(249) H. Fol. " Sur le developpement des Pteropodes." Archives de Zool. experim. et gtntrale, Vol. iv. 1875.
 
(250) H. Fol. " Sur le developpement des Gasteropodes pulmones." Compt.
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(251) H. Fol. "Sur le developpement des Heteropodes." Archives de Zool.
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(252) C. Gegenbaur. "Beit. z. Entwicklungsgesch. der Landgasteropoden."
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(253) C. Gegenbaur. Untersuch. iib. Pteropoden u. Hetcropoden. Leipzig,
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(254) H. von Jhering. "Entwicklungsgeschichte von Helix." Jcnaische Zcitschrift, Vol. IX. 1875.
 
(255) W. Keferstein and E. Ehlers. "Beob. lib. d. Entwick. v. Molis
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(256) J. Koren and D. C. Danielssen. "Benuerk. til Mollusk. Udvikling."
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(257) J. Koren and D. C. Danielssen. liidrag til Pectinibr. Udvikl. licrgcn,
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(258) A. Krohn. "Beobacht. aus d. Entwickl. der Pteropoden u. Heterop."
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(259) A. Krohn. Beitr. zur Entwickl. der Pteropoden u. Heteropoden. Leipzig,
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(260) H. de Lacaze-Duthiers. "Mem. sur 1'anat.et 1'embryog. des Vermets."
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(261) P. Langerhans. "Zur Entwickl. der Gasterop. Opisthobr." Zeitschr.
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BIBLIOGRAPHY. xi
 
 
 
. E. R. Lankester. "On the development of the Pond-Snail." Quart.
 
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(263) E. R. Lankester. "On the coincidence of the blastopore and anus in
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(264) F. Leydig. "Ueber Paludina vivipara." Zeitschr. f. w. Zool., Vol. 11.
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(265) J. MUller. Ueber Synapta dig. u. iib. d. Erzeug. v. Schnecken in Holoth.,
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(266) J. Miiller. "Bemerk. aus d. Entwickl. der Pteropoden." Monatsber.
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(267) C. Rabl. "Die Ontogenie d. Siisswasser-Pulmonaten." Jenaische Zeitschrift, Vol. IX. 1875.
 
(268) C. Rabl. "Ueb. d. Entwick. d. Tellerschnecke (Planorbis)." Morph.
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(269) W. Salensky. " Beitr. zur Entwickl. d. Prosobr." Zeitschr. f. iv. Zool. ,
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(270) O. Schmidt. "Ueb. Entwick. von Limax agrestis." Miillcr's Archiv,
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(271) Max S. Schultze. "Ueber d. Entwick. des Tergipes lacinulatus."
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(272) E. Selenka. "Entwick. von Tergipes claviger." Niederl. Arch.f. Zool.,
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(273) E. Selenka. "Die Anlage d. Keimbl. bei Purpura lapillus." Niederl.
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(274) C. Semper. "Entwickl. der Ampullaria polita, etc." Natuurk. Verhandl. Utrechts Genootsch., 1862.
 
(275) An. Stecker. "Furchung u. Keimblatterbildung bei Calyptraa."
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(276) A.Stuart. " Ueb. d. Entwickl. einiger Opisthobr." Zeitschr. f. w. Zool.,
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(277) N. A. Warneck. "Ueber d. Bild. u. Entwick. d. Embryos bei Gasterop." Bullet. Soc. natural, de Moscou, T. xxm. 1850.
 
Cephalopoda.
 
(278) P. J. van Beneden. " Recherches sur 1'Embryogenie des Sepioles."
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(279) N. Bobretzky. Observation on the Development of the Cephalopoda
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(280) H. Grenacher. " Zur Entwicklungsgeschichte d. Cephalopoden." Zeit.
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(281) A. K6 Hiker. Entwicklungsgeschichte d. Cephalopoden. Zurich, 1844.
 
(282) E. R. Lankester. "Observations on the development of the Cephalopoda." Quart. J. of Micr. Science, Vol. xv. 1875.
 
(283) E. Metschnikoff. " Le developpement des Sepioles." Archives d. Sc.
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Polyplacophora.
 
(284) A. Kowalevsky. "Ueb. d. Entwick. d. Chitonen." Zoologischer
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(285) S L. Loven. " Om utvecklingen hos sliigtet Chiton." Stockholm
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Scaphopoda.
 
(286) H. Lacaze-Duthiers. "Developpement du Dentale." Ann. d. Sci.
 
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Lamellibranchiata.
 
(287) M. Braun. " Postembryonale Entwicklung d. Susswasser-Muscheln."
 
Zoologischer Garten.
 
 
 
xii BIBLIOGRAPHY.
 
 
 
(288) C. G. Carus. " Neue Untersuch. lib. d. Entvvickl. unscrer FlussmuVcrh. Leop.-Car. Akad., Vol. xvi. 1832.
 
(289) W. Flemming. " Studien in d. Entwicklungsgeschichte der Najadcn."
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(290) F. Ley dig. " Ueber Cyclas Cornea." Miiller's Archiv, 1855.
 
(2111) S. L. Loven. " Bidrag til Kanned. om Utveckl. af Moll. Acephala
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(292) C. Rabl. "Ueber d. Entwicklungsgeschichte d. Malermuschel." Jenaische Zeitschrift, Vol. X. 1876.
 
(293) W. Salensky. " Bemerkungen uber Haeckels Gastraea-Theorie (Ostrea)."
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(294) O. Schmidt. " Ueb. d. Entwick. von Cyclas calyculata." Muller's
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(295) O. Schmidt. "Zur Entwickl. der Najaden." Wien. Sitzungsber.
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(296) P. Stepanoff. " Ueber die Geschlechtsorgane u. die Entwicklung von
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(297) H. Lacaze-Duthiers. " Ueveloppement d. branchies d. Mollusques
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POLYZOA.
General.
 
(298) J. Barrois. Recherches sur Cembi yologie des Bryozoaires. Lille, 1877.
 
Entoprocta.
 
(299) B. Hatschek. " Embryonalentwicklung u. Knospung d. Pedicellina
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(300) M. Salensky. " Etudes sur les Bryozoaires entoproctes." Ann. Scien.
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(301) O. Schmidt. "Die Gattung Loxosoma." Archivf. mik. Anat.,Rd.
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(302) C. Vogt. "Sur le Loxosome des Phascolosomes." Archives de Zool.
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(303) C. Vogt. "Bemerkungen zu Dr Hatschek's Aufsatz lib. Embryonalentwicklung u. Knospung von Pedicellina echinata." Zeit. f. wiss. Zool., Bd. XXX.
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Ectoprocta.
 
(304) G. J. A 11 man. Monograph of fresh water Polyzoa. Ray Society.
 
(305) G. J. Allman. " On the structure of Cyphonautes." Quart. J. of Micr.
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(306) G. J. Allman. "On the structure and development of the Phylactola>
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(307) J. Barrois. " Le developpement d. Bryozoaires Chilostomes." Comptes
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(308) E. Claparede. " Beitrage zur Anatomic u. Entwicklungsgeschichte d.
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(309) E. Claparede. "Cyphonautes." Anat. u. Entwick. wirbell. Thiere.
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(310) R. E. Grant. "Observations on the structure and nature of Flustrae."
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(311) B. Hatschek. "Embryonalentwicklung u. Knospung d. Pedicellina
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(312) T. II. Huxley. "Note on the reproductive organs of the Cheilostome
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(313) L. Joliet. "Contributions a 1'histoire naturelle des Bryozoaires des
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(314) E. Metschnikoff. " Ueber d. Metamorphose einiger Seethiere." Gottingische Nachrichten, 1869.
 
 
 
BIBLIOGRAPHY. xiii
 
 
 
(315) E. Metschnikoff. Bull. deTAcad. de St Pttersbourg, XV. 1871, p. 507.
 
(316) H. Nitsche. " Beitrage zur Kenntniss d. Bryozoen." Zrit. f. wiss.
 
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(317) W. Repiachoff. "Zur Naturgeschichte d. chilostomen Seebryozoen."
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(318) W. Repiachoff. " Ueber die ersten Entwicklungsvorgange bei Tendra
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(319) W. Repiachoff. "Zur Kenntniss der Bryozoen." Zoologischer Anzeiger, No. 10, Vol. i. 1878.
 
(320) W. Repiachoff. " Bemerkungen lib. Cyphonautes. " Zoologischer Anzeiger, Vol. n. 1879.
 
(321) M. Salensky. " Untersuchung an Seebryozoen." Zeit. fur wiss. Zool..
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(322) A. Schneider. "Die Entwicklung u. syst. Stellung d. Bryozoen u.
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(323) Smitt. " Om Hafsbryozoernas utveckling och fettkroppar. " Aftryck ur
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(324) T. Hincks. British Marine Polyzoa. Van Voorst, 1880.
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BRACHIOPODA.
 
(325) W. K. Brooks. " Development of Lingula." Chesapeake Zoological
Laboratory, Scientific Results of the Session of 1878. Baltimore, J. Murphy and Co.
 
(326) A. Kowalevsky. "Development of the Brachiopoda." Protocol of the
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(327) H. Lacaze-Duthiers. " Histoire de la Thecidie." Ann. Scien. Nat.
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(328) Morse. " On the Early Stages of Terebratulina septentrionalis." Mem.
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(329) Morse. "On the Embryology of Terebratulina." Mem. Boston Soc.
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(330) Morse. " On the Systematic Position of the Brachiopoda." Proceedings
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(331) Fritz Miiller. " Beschreibung einer Brachiopoden-Larve." Miiller's
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CKLETOPODA.
 
(332) Alex. Agassiz. "On the young stages of a few Annelids." Annals
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(333) Alex. Agassiz. " On the embryology of Autolytus cornutus and alternations of generations, etc." Boston Journal of Nat. History, Vol. VH. 1859-63.
 
(334) W. Busch. Beobachtungen it. Anaf. u. Entwick. einiger wirbelloser Seethiere, 1851.
 
(335) Ed. Claparede. Beobachtungen u. Anat. u. Entwick. 'wirbelloser Thiert
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(337) E. Grube. Untersuchungen ub. Entivicklung d. Anneliden. Komgsberg,
 
4 (338) B. Hatschek. " Beitrage z. Entwick. u. Morphol. d Anneliden." Si/*.
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OwQ
 
(340) Th. H. Huxley. "On hermaphrodite and fissiparous species of tubicolar Annelidse (Protula)." Edinburgh New Phil. Journal, Vol. I. 1855.
 
(341) N. Kleinenberg. "The development of the earthworm Lumbncus
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XIV BIBLIOGRAPHY.
 
 
 
(342) A. Kowalevsky. " Embryologische Studien an Wiirmern u. Arthropoden." Mem. Acad. Pttersbourg, Series VH. Vol. xvi. 1871.
 
(343) A. Krohn. " Ueber die Erscheinungen bei d. Fortpfianzung von Syllis
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(347) M. Milne- Ed\vards. " Recherches zoologiques, etc." Ann. Scie.
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(348) J. Miiller. "Ueb. d. Jugendzustande einiger Seethiere." Monats. d.
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(349) Max Miiller. "Ueber d. weit. Entwick. von Mesotrocha sexoculata."
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(357) M. Stossich. " Beitrage zur Entwicklung d. Chaetopoden." Sitz. d. k.
k. Akad. Wiss. Wien, B. LXXVII. 1878.
 
(358) R. v. Willemoes-Suhm. " Biologische Beobachtungen ii. niedrige
Meeresthiere." Zeit.f. wiss. Zool. Bd. xxi. 1871.
 
DlSCOPHORA.
 
(359) O. BUtschli. " Entwicklungsgeschichtliche Beitrage (Nephelis)." Zeit.
f. wiss. Zool. Vol. xxix. 1877.
 
(360) E. Grube. Untersuchungen ub. d. Entwicklung d. Anneliden. Konigsberg, 1844.
 
(361) C. K. Hoffmann. "Zur Entwicklungsgeschichte d. Clepsineen." NICderland. Archiv f. Zool. Vol. IV. 1877.
 
(362) R. Leuckart. Die menschlichen Parasiten (Hirudo}, Vol. I. p. 686,
et seq.
 
(363) H. Rathke. Beit. z. Entwicklungsgesch. d. Hirudineen. Leipzig, 1862.
 
(364) Ch. Robin. Mem. snr le Developpement embryogenique des Ilirndiih'c*.
Paris, 1875.
 
(365) C. O. Whitman. "Embryology of Clepsine." Quart. J. of Micro.
Science, Vol. xvm. 1878.
 
[ Vide also C. Semper (No. 355) and Kowalevsky (No. 342) for isolated observations.]
 
GEPHYREA.
GepJiyrea nuda.
 
(366) A. Kowalevsky. Sitz. d. zool. Abth. d. Iff. Versam. rtiss. Naturf
(Thalassema). Zeit.f. wiss. Zool. Vol. xxn. 1872, p. 284.
 
(367) A. Krohn. "Ueb. d. Larve d. Sipunculus nudus ncbst I'.c UK iknii^cn, '
etc. Miiller's Archiv, 1857.
 
 
 
BIBLIOGRAPHY. xv
 
 
 
(368) M. Salensky. " Ueber die Metamorphose d. Echiurus." Morfhohgisches
Jahrbuch, Bd. 11.
 
(369) E. Selenka. "Eifurchung u. Larvenbilflung von Phascolosoma elongatum." Zeit.f. wiss. Zool. 1875, Bd- xxv. p. i.
 
(370) J. W. Spengel. " Beitrage z. Kenntniss d. Gephyreen (lionellia)."
MitlheiL a. d. zool. Station z. Neapel, Vol. i. 1879.
 
Gephyrea tubicola (Actinotroc/ia).
 
(371) A. Krohn. " Ueb. Pilidium u. Actinotrocha." Muller's Archiv, 1858.
 
(372) A. Kowalevsky. " On anatomy and development of Phoronis," Petersburg, 1867. i PI. Russian. Vide Leuckart's Bcricht, 1866-7.
 
(373) E. Metschnikoff. " Ueber d. Metamorphose einiger Seethiere (Actinotrocha)." Zeit.f. wiss. Zool. Bd. XXI. 1871.
 
(374) J. Miiller. " Bericht ub. ein. Thierformen d. Nordsee." Muller's Archiv,
1846.
 
(375) An. Schneider. "Ueb. d. Metamorphose d. Actinotrocha branchiata."
Muller's Arch. 1862.
 
CH^TOGNATHA.
 
(376) O. Butschli. " Zur Entwicklungsgeschichte der Sagitta." Zeilschrifl f.
wiss. Zool., Vol. xxin. 1873.
 
(377) C. Gegenbaur. "Ueber die Entwicklung der Sagitta." Abhand. d.
natiirforschenden Gesellschaft in Halle, 1857.
 
(378) A. Kowalevsky. " Embryologische Studien an Wiirmern u. Arthropoden." Mem. Acad. Petersbourg, vn. ser., Tom. xvi., No. 12. 1871.
 
MYZOSTOMEA.
 
(379) L.Graff. Das Genus Myzostoma. Leipzig, 1877.
 
(380) E. Metschnikoff. "Zur Entwicklungsgeschichte d. Myzostomum."
Zeit.f. wiss. Zool., Vol. xvi. 1866.
 
(381) C. Semper. "Z. Anat. u. Entwick. d. Gat. Myzostomum." Zeit.f.
wiss. Zool., Vol. IX. 1858.
 
GASTROTRICHA.
 
(382) H. Ludwig. " Ueber die Ordnung Gastrotricha Metschn." Zeit.f. wiss.
Zool., Vol. xxvi. 1876.
 
NEMATELMINTHES.
 
(383) O. Butschli. "Entwicklungsgeschichte d. Cucullanus elegans." Zeit.
f. wiss. Zool., B. xxvi. 1876.
 
(384) T. S. Cobbold. Entozoa. Groombridge and Son, 1864.
 
(385) T. S. Cobbold. Parasites; a Treatise on the Entozoa of Man and
Animals. Churchill, 1879.
 
(386) O. Caleb. "Organisation et developpement des Oxyurides, etc.
Archives de Zool. exper. et gener., Vol. VII. 1878.
 
(387) R. Leuckart. Untersuchungeniib. Trichina spiralis. 2nd ed. Leipzig,
1866.
 
(388) R. Leuckart. Die menschlichen Parasiten, Bd. u. 1876.
 
(389) H. A. Pagenstecher. Die Trichinen nach Versuchen dargestellt.
 
(390) A.Schneider. Monographie d. Nematoden. Berlin, 1866.
 
(391) A. Villot. " Monographie des Dragoneaux " (Gordioidea). Archives de
Zool. exptr. et gtner., Vol. in. 1874.
 
ACANTHOCEPHALA.
 
(392) R. Greeff. " Untersuchungen u. d. Ban u. Entwicklung des Echin.
miliarius." Archiv f. Naturgesch. 1864.
 
(393) R. Leuckart. Die menschlichen Parasiten. Vol. 11. p Soi ol
 
 
 
xvi BIBLIOGRAPHY.
 
 
 
(394) An. Schneider. " Ueb. d. Bau d. Acanthocephalen." Archiv f. Anat.
w. Phys. 1868.
 
(395) G. R. Wagener. Beitrdge z. Entrvicklungsgeschichte d. Eingeweidewiirmer. Haarlem, 1865.
 
TRACHEATA.
 
PRO TO TRA CHE A TA .
 
(396) H. N. Moseley. "On the Structure and Development of Peripatus
capensis." Phil. Trans. Vol. 164, 1874.
 
MYRIAPODA.
 
(397) G. Newport. "On the Organs of Reproduction and Development of the
Myriapoda." Philosophical Transactions, 1841.
 
(398) E. Metschnikoff. " Embryologie der doppeltfiissigen Myriapoclen
(Chilognatha)." Zeit.f. wiss. Zool., Vol. xxiv. 1874.
 
(399) E. Metschnikoff. " Embryologisches iiber Geophilus." Zeit. f. wiss.
'Zool., Vol. xxv. 1875.
 
(400) Anton Stecker. "Die Anlage d. Keimblatter bei den Diplopoden."
Archiv f. mik. Anatomic, Bd. xiv. 1877.
 
INSECTA.
 
(401) M Balbiani. " Observations s. la reproduction d. Phylloxera du Chene."
An. Sc. Nat. Ser. v. Vol. xix. 1874.
 
(402) E. Bessels. "Studien u. d. Entwicklung d. Sexualdrtisen bei den Lepidoptera." Zeit.f. miss. Zool. Bd. xvn. 1867.
 
(403) Alex. Brandt. " Beitrage zur Entwicklungsgeschichte d. Libellulida u.
Hemiptera, mit besonderer Beriicksichtigung d. Embryonalhiillen derselben." Mem.
Ac. Pttersbourg, Ser. vn. Vol. xin. 1869.
 
(404) Alex. Brandt. Ueber das Ei u. seine Bildungsstdtte. Leipzig, 1878.
 
(405) O. Butschli. " Zur Entwicklungsgeschichte d. Biene." Zeit. f. wiss.
Zool. Bd. xx. 1870.
 
(406) H. Dewitz. "Bau u. Entwicklung d. Stachels, etc." Zeit.f. wiss. Zool.
Vols. xxv. and xxvin. 1875 and 1877.
 
(407) H. Dewitz. "Beitrage zur Kenntniss d. Postembryonalentwicklung d.
Gliedmassen bei den Insecten." Zeit. /. wiss. Zool. xxx. Supplement. 1878.
 
(408) A. Dohrn. "Notizen zur Kenntniss d. Insectenentwicklung." Zeitschriftf. wiss. Zool. Bd. xxvi. 1876.
 
(409) M. Fabre. " L'hypermetamorphose et les mceurs des Meloides." An.
Sci. Nat. Series iv. Vol. vn. 1857.
 
(410) Ganin. "Beitrage zur Erkenntniss d. Entwicklungsgeschichte d. Insecten." Zeit. f. wiss. Zool. Bd. xix. 1869.
 
(411) V. Graber. Die Insecten. Miinchen, 1877.
 
(412) V. Graber. " Vorlauf. Ergeb. lib. vergl. Embryologie d. Insecten."
Archiv f. mikr. Anat. Vol. XV. 1878.
 
(413) O.v.Grimm. " Ungeschlechtliche Fortpflanzung einer Chironomus-Art
u. deren Entwicklung aus dem unbefruchteten Ei." Mhn. Acad. Pttcrsbourg. 1X70.
 
(414) B. Ilatschek. " Beitrage zur Entwicklung d. Lepidopteren." Jenaischc
Zeitschrift, Bd. xi.
 
(415) A. Kollikcr. " Observationes de prima insectorum gcnese, etc. " Ann.
Sc. Nat. Vol. xx. 1843.
 
(11(5) A. Kowalevsky. " Embryologische Studien an Wiirmern u. Arthropoden." Mtm. Ac. imp. J\'(,-rstn>nr, Ser. VII. Vol. XVI. iSji.
 
(417) C. Kraepelin. " Untersuchungen lib. d. Bau, Mechanismus u. d.
Entwick. des Stachels d. l.icnartigai Tliicrc." Zeit.f. wiss. Zool. Vol. xxm. 1X7.5.
 
(418) C. Kupffcr. " Faltcnblatt nn d. Embryoncn d. Gattung Chirononnis."
Arch.f. mikr. Anat. Vol. n. iS66.
 
(419) R. Leuckart. Zur Kemituiss d. Gi'ncratiomxi'ffhscls it. d. /'/; -Ihetii^ , <
b. d. Insecten. Frankfurt, iH.nS.
 
 
 
BIBLIOGRAPHY. xvii
 
 
 
(420) Lubbock. Origin and Metamorphosis of Insi-cts. 1874.
 
(421) Lubbock. Monograph on Collembola ami Thysanura. Ray Society,
1873
(422) Melnikow. " Beitrage z. Embryonalentwicklung d. Insecten." Archiv
f. Naturgeschichte, Bd. XXXV. 1869.
 
(423) E. Metschnikoff. ' ' Embryologische Studien an Insecten." '/.fit. /.
wiss. Zool Bd. xvi. 1866.
 
(424) P. Meyer. " Ontogenie und Phylogenie d. Insecten." Jcnaischt Zfitschrift, Vol. X. 1876.
 
(425) Fritz Miiller. " Beitrage z. Kenntniss d. Termiten." Jcnaische Zeitschrift, Vol. IX. 1875.
 
(426) A. S. Packard. " Embryological Studies on Diplex, Perithemis, and the
Thysanurous genus Isotoma." Mem. Pea body Acad. Science, \. 2. 1871.
 
(427) Suckow. " Geschlechtsorgane d. Insecten." Heusinger's Zeitschrift f.
organ. Physik, Bd. II. 1828.
 
(428) Tichomiroff. " Ueber die Entwicklungsgeschichte des Seidenwiirms."
Zoologischer Anzeigcr, n. Jahr. No. 20 (Preliminary Notice).
 
(429) Aug. Weismann. "Zur Embryologie d. Insecten." Arehiv f. Anat.
und Phys. 1864.
 
(430) Aug. Weismann. " Entwicklung d. Dipteren." Zeit. f. wiss. Zool.
Vols. xni. and xiv. Leipzig, 1863 4.
 
(431) Aug. Weismann. " Die Metamorphose d. Corethra plumicornis." Ztit.
f. unss. Zool. Vol. xvi. 1866.
 
(432) N. Wagner. " Beitrag z. Lehre d. Fortpflanzung d. Insectenlarven."
Zeit.f. wiss. Zool. Vol. Xlll. 1860.
 
(433) Zaddach. Untersuchnngen tib. d. Bau u. d. Enhuicklung d. Gliederlhifre.
Berlin, 1854.
 
ARACHNID A.
Scorpionidce.
 
(434) El. Metschnikoff. " Embryologie des Scorpions." Zeit.f. unss. Zool.
Bd. xxi. 1870.
 
(435) H. Rathke. Reisebemerknngen aus Taurien (Scorpio), Leipzig, 1837.
 
Pseudoscorpionidce.
 
(436) El. Metschnikoff. " Entwicklungsgeschichte d. Chelifer." Zeit.f. unss.
Zool. Bd. xxi. 1870.
 
(437) A. Stecker. "Entwicklung der Chthonius-Eier im Mutterleibe und c
Bildung des Blastoderms." Sitzung. konigl. bohmisch. Gesellschaft Wissensch. t 1876,
3. Heft, and Annal. and Mag. Nat. History, 1876, xvill. 197.
 
Phalangida.
 
(438) M. Balbiani. " Memoire sur le developpement des Phalangides." Ann.
Scien. Nat. Series v. Vol. xvi. 1872.
 
Araneina.
 
(439) M. Balbiani. "Memoire sur le developpement des Araneides." Ann.
Scien. Nat. Series v. Vol. xvn. 1873. /->./
 
(440) F. M. Balfour. "Notes on the development of the Arane
 
Journ. of Micr. Science, Vol. XX. 1880. v ,
 
(441) J. Barrois. " Recherches s. 1. developpement des Araign^es.
 
de I' Anat. et de la Physiol. 1878. , , fiA
 
(442) E. Claparede. Recherches s. revolution des Aratgnees. Jtrecht, 1862.
 
(443) Her old. De generation Araneorum in Ovo. Marburg, 1824.
 
(444) H. Ludwig. "Ueber die Bildung des Blastoderms bei den
Zeit.f. wiss. Zool. Vol. xxvi. 1876.
 
B. II. b
 
 
 
xviii BIBLIOGRAPHY.
 
 
 
Acariua.
 
(445) P. van Beneden. " Developpement de 1'Atax ypsilophora." Acad. Bruxelles, t. xxiv.
 
(446) Ed. Claparede. "Studien uber Acarinen." Zeit. /. wits. Zoo/., Bd.
xvin. 1868.
 
CRUSTACEA.
General Works.
 
(447) C. Spence Bate. " Report on the present state of our knowledge of the
Crustacea." Report of the British Association for 1878.
 
(448) C. Claus. Untersuchungen zur Erforschung der genealogischen Grundlage
des Crustaceen -Systems. Wien, 1876.
 
(449) A. Dohrn. "Geschichte des Krebsstammes. " Jenaische Zeitschrift,
Vol. vi. 1871.
 
(450) A. Gerstaecker. Bronris Thierreich, Bd. v. Arthropoda, 1866.
 
(451) Th. II. Huxley. The Anatomy of Invertebrated Animals. London,
1877.
 
(452) Fritz Miiller. Fiir Darwin, 1864. Translation, Facts for Darwin.
London, 1869.
 
Branchiopoda.
 
(453) Brauer. "Vorlaufige Mittheilung iiber die Entwicklung u. Lebensweise
des Lepidurus (Apus) productus." Sitz. der Ak. d. Wiss. Wien, Vol. LXIX., 1874.
 
(454) C. Claus. ' Zur Kenntniss d. Baues u. d. Entwicklung von Branchipus
stagnalisu. Apuscancriformis." Abh. d. konig. Gesell. der Wiss. Gbttingen, Vol. xviii.
 
l8 '3-_
 
(455) C. Grobben. "Zur Entwicklungsgeschichte d. Moina rectirostris."
Arbeit, a. d. zoologisch. Institute Wier., Vol. II., 1879.
 
(456) E. Grube. " Bemerkungen iiber die Phyllopoden nebst einer Uebersicht
etc." Archivf. Naturgcschichte, Vol. xix., 1853.
 
(457) N. Joly. " Histoire d'un petit Crustace (Artemia salina, Leach) etc." Annales d. Sciences Natur., 2nd ser., Vol. xiir., 1840.
 
(458) N. Joly. " Recherches zoologiques anatomiques et physiologiques sur
1' I sauracy clad oides ( = Esther ia) nouveau genre, etc." Annales d. Sciences Nat., 2nd
ser., Vol. xvii., 1842.
 
(459) Lereboullet. " Observations sur la generation et le de veloppement de la
Limnadia de Hermann." Annales d. Sciences Nattir., ^th ser., Vol. v., 1866.
 
(460) F. Ley dig. " Ueber Artemia salina u. Branchipus stagnalis." Zeit. f.
wiss. Zool., Vol. in., 1851.
 
(461) G. O. Sars. "Om en dimorph Udvikling samt Generationsvexel hos
I^eptodora." Vidensk. Selskab. For hand, 1873.
 
(462) G. Zaddach. De apodis cancrefortnis Schaeff. anatome ct historia evolutionis. Dissertatio inanguralis zootomica. Bonnae, 1841.
 
 
 
Nebaliadce.
 
(463) C. Claus. " Ueber den Bau u. die systematische Stellung von Nebalia."
Zeit.f. wiss. Zool., 15d. xxn. 1872.
 
(464) E.Metschnikoff. Development of Nebalia ( Russian), 1 868.
 
Schizopoda.
 
(465) E. van Beneden. "Recherches sur 1'Embryogenie des Crustace's. u.
Developpement des Mysis." liullet. de rAcadc ! mie roy. de Belgique, second series,
Tom. xxvin. 1869.
 
(46H) C. Claus. " Ueber einige Schizopoden u. niedere Malakostraken." Zeit.
/. -t'tss. Zoologie, Bd. XIII., 1863.
 
 
 
BIBLIOGRAPHY. xix
 
 
 
(467) A. Dohrn. " Untersuchungen iib. Bau u. Entwicklung d. Arthropoden."
Zeit. f. wiss. Zool., Bd. xxi., 1871, p. 375. Peneus zoaea (larva of Euphausia).
 
(468) E. Metschnikoff. " Ueber ein Larvenstadium von Euphausia." Zeit.
fiir wiss. Zool., Bd. xix., 1869.
 
(469) E. Metschnikoff. " Ueber den Naupliuszustand von Euphausia." Zeit.
fiir wiss. Zool., Bd. xxi., 1871.
 
Decapoda.
 
(470) Spence Bate. "On the development of Decapod Crustacea." Phil.
Trans., 1858.
 
(471) Spence Bate. " On the development of Pagurus." Ann. and Mag. Nat.
History, Series 4, Vol. 1 1., 1868.
 
(472) N. Bobretzky. Development of Astacus and Paluemon. Kiew, 1873.
(Russian.)
 
(473) C. Claus. "Zur Kenntniss d. Malakostrakenlarven." Wiirzb. naturw.
Zeitschrift, 1861.
 
(474) R. Q. Couch. "On the Metamorphosis of the Decapod Crustaceans."
Report Cornwall Polyt. Society, 1848.
 
(475) Du Cane. "On the Metamorphosis of Crustacea." Ann. and Mag. of
Nat. History, 1839.
 
(476) Walter Faxon. " On the development of Paloemonetes vulgaris." Bull.
of the Mus. of Comp. Anat. Harvard, Cambridge, Mass., Vol. V., 1879.
 
(477) A. Dohrn. " Untersuchungen iib. Bau u. Entwicklung d. Arthropoden."
" Zur Entwicklungsgeschichte der Panzerkrebse. Scyllarns Palinurus." Zeit. f.
wiss. Zool., Bd. xix., 1870.
 
(478) A. Dohrn. "Untersuchungen iib. Bau u. Entwicklung d. Arthropoden.
Erster Beitrag z. Kenntniss d. Malacostrakcn u. ilirer Larven Amphion Reynaudi,
Lophogaster, Portunus, Porcellanus, Elaphocaris. " Zeit. f. ^viss. Zool., Bd. XX.,
1870.
 
(479) A. Dohrn. "Untersuchungen iib. Bau u. Entwicklung d. Arthropoden.
Zweiter Beitrag, etc." Zeit.f. wiss. Zool., Bd. XXI., 1871.
 
(480) N. J oly. " Sur la Caridina Desmarestii." Ann. Scien. Nat., Tom. xix.,
1843.
 
(481) Lereboullet. " Recherches d. 1'embryologie comparee sur le developpement du Brochet, de la Perche et de 1'Ecrevisse." Mem. Savuns Etrang. Paris, Vol.
xvii., 1862.
 
(482) P. Mayer. "Zur Entwicklungsgeschichte d. Dekapoden." Jenaische
Zeitschrift, Vol. XI., 1877.
 
(483) Fritz Miiller. '* Die Verwandlung der Porcellana." Archivf. Naturgeschichte, 1862.
 
(484) Fritz Miiller. " Die Verwandlungen d. Garneelen." Archivf. Naturgesch., Tom. xxix.
 
(485) Fritz Miiller. " Ueber die Naupliusbrut d. Garneelen." Zeit. f. wiss.
Zool., Bd. xxx., 1878.
 
(486) T. J. Parker. "An account of Reichenbach's researches on the early
development of the Fresh-water Crayfish." Quart. J. of M. Science, Vol. xvui.,
1878.
 
(487) H. Rathke. Ueber die Bildung u. Entwicklung d. Flusskrebses. Leipzig, 1829.
 
(488) H. Reichenbach. " Die Embryoanlage u. erste Entwicklung d. Flusskrebses." Zeit. f. wiss. Zool., Vol. xxix., 1877.
 
(489) F. Richters. "Ein Beitrag zur Entwicklungsgeschichte d. Loricaten."
Zeit.f. wiss. Zool., Bd. xxiii., 1873.
 
(490) G. O. Sars. " Om Hummers postembryonale Udvikling." Vidcnsk Selsk.
Forh. Christiania, 1874.
 
(491) Sidney J. Smith. " The early stages of the American Lobster. " Tratts.
of the Connecticut Acad. of Arts and Sciences, Vol. II., Part i, 1873.
 
(492) R. v. Willemoes Suhm. " Preliminary note on the development of some
pelagic Decapoda." Proc. of Royal Society, 1876.
 
 
 
XX BIBLIOGRAPHY.
 
 
 
Stomatopoda.
 
(41KI) \V. K. Brooks. " On the larval stages of Squilla empusa.'' Chesapeake
Zoological Laboratory^ Scientific results of the Session ^1878. Baltimore, 1879.
 
(494) C. Claus. "Die Metamorphose der Squilliden." Abhand. dcr konigl.
Gesell. der IViss. ztt Gottingen^ 1*7-.
 
( 1 '.!">) Fr. M tiller. 4i Bruchstuck a. der Entwicklungsgeschichte d. Maulfiisser I.
und II." Archivf. Naturgeschichte, Vol. xxvni., 1862, and Vol. XXIX., 1863.
 
Cumacea*
 
( 1%) A. Dohrn. " Ueber den Bau u. Entwicklung d. Cumaceen." Jenaische
Zeitschrift, Vol. v., 1870.
 
hopoda.
 
(497) Ed. van Beneden. " Recherches sur 1'Embryogenie des Crustaces. i.
Asellus aquaticus." BiuL de FAcad. roy. Belgique, 2me serie, Tom. XXVIII., No. 7,
1869.
 
(498) N. Bobretzky. "Zur Embryologie des Oniscus murarius." Ztit. fur
wiss. Zool., Bd. xxiv., 1874.
 
(4119) J. F. Bullar. "On the development of the parasitic Isopoda." Phil.
Trans., Part n., 1878.
 
(500) A. Dohrn. " Die embryonale Entwicklung des Asellus aquaticus." Zeit.
f. wiss. Zool., Vol. xvii., 1867.
 
(501) II. Rathke. Untersuchungen iibcr die Bildung und Entwicklung der
VVasser-Assel. Leipzig, 1832.
 
(5u2) H. Rathke. Zur Morphologic. Reisebemerkungen aus J^aurien. Riga u.
Leipzig, 1837. (Bopyrus, Idothea, Ligia, lanira.)
 
. A mphipoda.
 
(503) Ed. van Beneden and E. Bessels. "Memoire sur la formation du
blastoderme chez les Amphipodes, les Lerneens et les Copepodes." Classe des Sciences
de F Acad. roy. de Belgiqtie, Vol. xxxiv., 1868.
 
(004) De la Valette St George. " Studien liber die Entwicklung der Amphipoden." Abhand. d. naturfor. Gesell. zu Halle, Bd. v., 1860.
 
Copcpoda.
 
(505) E. van Beneden and E. Bessels. "Memoire sur la formation du blastoderme chez les Amphipodes, les Lerneens et Copepodes." Classe des Sciences dc
FAcad. roy. de Bel^ique, Vol. xxxiv., 1868.
 
(">(Hi) E. van Beneden. " Recherches sur 1'Embryoge'nie des Crustaces I v. Anchorella, Lerneopoda, Branchiella, Hessia." Bull, de FAcad. roy. de Belgique^ sme
serie, T. xxix., 1870.
 
(507) C. Claus. Zur Anatomie u. Entwicklungsgeschichte d. Copepoden.
 
("iii.S) C. Claus. " Untcrsuchungen iiber die Organisation u. N'crwaiulschaft d.
Copepoden." Witrzburger nalttnviss. Zeitschrift, Bd. ill., 1862.
 
(.")('.() C. Claus. ' Ueber den Bau u. d. Entwicklung von Achtheres percarum."
'/.cit.f. wiss. Zool., Bd. XI., 1862.
 
I ."> 1 ( i ) C . (' 1 a u s. Die frcilcbcnden Copepoden mit bcsonderer Beritcksichtigiing der
Fauna Dcutschlands, der Nordsec u. des Mitteltnecres. Leip/.i.^, 1863.
 
(511) C. C laus. " Ueber d. Entwicklung, Organisation u. systematische Stellung
d. Arguliihv." /.eit. f. wiss. tool., P>d. xxv., 1875.
 
(51^) P. P. C. Hoek. "Zur Entwicklungsgeschichte d. Entomostracen." Niederliindischcs Archiv, Vol. IV., 1877.
 
(513) N o rd m a n n. Mikrographische Beitrdge zur Naturgeschichte der ivirbcllosen
Thiert Z\\ cites Heft. 1832.
 
|.">M) Salensky. " Sphseronella Leuckartii." Archivf. Naturgcschichtc, 1868.
 
(515) F. Vejdovsky. "Untersuchnngen lib. d. Anat. u. Mctamorph. v. Trachcliastes polycolpus " Zcit.f. wiss. Zool., Vol. xxix., 1877.
 
 
 
BIBLIOGRAPHY. xxi
 
 
 
Cirripedia.
 
(516) C. Spence Bate. "On the development of the Cirripedia." Annals
and Mag. of Natur. History. Second Series, vm., 1851.
 
(517) E. van Beneden. " Developpement des Sacculines." Bull, de F Acad.
roy. de Belg., 1870.
 
(518) C. Claus. Die Cypris-dhnliehe Larve der Cirripedien. Marburg, 1869.
 
(519) Ch. Darwin. A monograph of the sub-class Cirripedia, i Vols., Kay
Society, 1851 4.
 
(520) A. Dohrn. " Untersuchungen iibcr Bau u. Entwicklung d. Arthropoden
ix. Eine neue Naupliusform (Archizoea gigas)." Zeit. f. wiss. Zool., Bd. XX.,
1870.
 
(521) P. P. C. Hoek. "Zur Entwicklungsgeschichte der Entomostraken I.
Embryologie von Balanus." Wiederlandisches Archiv fur Zoologic, Vol. III., 1876 7.
 
(522) R. Kossmann. " Suctoria u. Lepadidze. Arbeiten a. d. zool.-zoot. Instituted. Univer. Wiirz., Vol. I., 1873.
 
(523) Aug. Krohn. " Beobachtungen iiber die Entwicklung der Cirripedien."
Wiegmanrfs Archiv fur Naturgesch., xxvi., 1860.
 
(524) E. Metschnikoff. Sitzungsberichte d. Versammlung deutscher Naturforscher zu Hannover ; 1865. (Balanus balanoides.)
 
(525) Fritz Muller. "Die Rhizocephalen." Archiv /. Naturgeschichte,
18623.
 
(526) F. C. Noll. "Kochlorine hamata, ein bohrendes Cirriped." Zeit.f. wiss.
Zool., Bd. xxv., 1875.
 
(527) A. Pagenstecher. " Beitrage zur Anatomic und Entwicklungsgeschichte
von Lepas pectinata." Zeit.f. wiss. Zoo/., Vol. xin., 1863.
 
(52tt) J. V. Thompson. Zoological Researches and Illustrations, Vol. I., Part I.
Memoir iv. On the Cirripedes or Barnacles. 8vo. Cork, 1830.
 
(529) J. V. Thompson. " Discovery of the Metamorphosis in the second type
of the Cirripedes, viz. the Lepades completing the natural history of these singular
animals, and confirming their affinity with the Crustacea." Phil. Trans. 1835. P art
n.
 
(530) R. von Willemoes Suhm. "On the development of Lepas fascicularis."
Phil. Trans., Vol. 166, 1876.
 
Ostracoda.
 
(531) C. Claus. " Zur naheren Kenntniss der Jugendformen von Cypris ovum."
Zeit.f. wiss. Zool., Bd. XV., 1865.
 
(532) C. Claus. "Beitrage zur Kenntniss d. Ostracoden. Entwicklungsgeschichte von Cypris ovum." Schriften d. Gesell. zur Bejorderung d. gesamm. Naturwiss. zu Marburg, Vol. IX., 1868.
 
PCECILOPODA.
 
(533) A. Dohrn. "Untersuch. lib. Bau u. Entwick. d. Arthropoden (Limulus
polyphemus)." Jcnaische Zeitschrift, Vol. VI., 1871.
 
(534) A. S. Packard. "The development of Limulus polyphemus." Mem.
Boston Soc. Nat. History, Vol. II., 1872.
 
PYCNOGONIDA.
 
(535) G. C a van n a. " Studie e ricerche sui Picnogonidi." PiMIicazioni del R.
Instittito di Studi super iori in Firenze, 1877.
 
(536) An. Dohrn. " Ueber Entwicklung u. Bau d. Pycnogoniden." Jenaische
Zeitschrift, Vol. v. 1870, and "Neue Untersuchungen ub. Pycnogoniden." Mittheil.
a. d. zoologischen Station zu Ncapel, Bd. I. 1878.
 
(537) G. Hodge. " Observations on a species of Pycnogon, etc." Annal. and
Mag. of Nat. Hist. Vol. ix. 1862.
 
(538) C. Semper. " Ueber Pycnogoniden u. ihre in Hydroiden schmarotzenden
Larvenformen. 1 ' Arbeiten a. d. zool.-zoot. Instit. IViiizburg, Vol. I. 1874.
 
 
 
xxii BIBLIOGRAPHY.
 
 
 
PENTASTOMIDA.
 
(539) P. T. van Ben e den. " Recherches s. 1'organisation et le developpement d.
Linguatules. Ann. d. Scien. Nat., 3 Ser., Vol. XI.
 
("I'M R. Leuckart. " Bau u. Entwicklungsgeschichte d. Pentastomen." Leipzig
and Heidelberg. 1860.
 
TARDIGRADA.
 
(541) J. Kaufmann. " Ueber die Entwicklung u. systematische Stellung d.
Tardigraden." Zeit.f. iviss. Zool., Bd. ill. 1851.
 
ECHINODERMATA.
 
(542) Alex. Agassiz. Revision of the Echini. Cambridge, U.S. 1872 74.
 
(543) Alex. Agassiz. " North American Starfishes." Memoirs of the Museum
of Comparative Anatomy and Zoology at Harvard College, Vol. v., No. i. 1877
(originally published in 1864).
 
(544) J. Barrois. " Embryogenie de 1'Asteriscus verruculatus " Journal de
VAnat. et Phys. 1879.
 
(545) A. Baur. Beitrdge zur Naturgeschichte d. Synapta digitata. Dresden,
1864.
 
(546) H. G. Bronn. Kiassen u. Ordnungen etc. Strahlenthiere, Vol. II. 1860.
 
(547) W. B. Carpenter. "Researches on the structure, physiology and development of Antedon." Phil. Trans. CLVI. 1866, and Proceedings of the Roy. Soc.,
No. 166. 1876.
 
(548) P. H. Carpenter. " On the oral and apical systems of the Echinoderms."
Quart. J. of Micr. Science, Vol. xvni. and xix. 1878 9.
 
(549) A. Gotte. " Vergleichende Entwicklungsgeschichte d. Comatula mediterranea." Arch.fiir micr. Anat., Vol. xn. 1876.
 
(550) R. Greeff. "Ueber die Entwicklung des Asteracanthion rubens vom Ei
bis zur Bipinnaria u. Brachiolaria." Schriftcn d. Gesellschaft zur Beforderung d. gesarnmlen Natnrwissenschaften zu Marburg, Bd. XII. 1876.
 
(551) R. Greeff. "Ueber den Bau u. die Entwicklung d. Echinodermen." Sitz.
d. Gesell. z. Beforderung d. gesam. Naturwiss. zu Marburg, No. 4. 1879.
 
(552) T. H. Huxley. "Report upon the researches of Mliller into the anat.
and devel. of the Echinoderms." Ann. and Mag. of Nat. Hist., 2nd Ser., Vol. vin.
 
(553) Koren and Danielssen. "Observations sur la Bipinnaria asterigera."
Ann. Scien. Nat., Ser. in., Vol. VII. 1847.
 
i-">l) Koren and Uanielssen. "Observations on the development of the Starfishes." Ann. and Mag. of Nat. Hist., Vol. XX. 1857.
 
(."..",.",) A. Kowalevsky. "Entwicklungsgeschichte d. Holothurien." Aft m. Ac.
Petersburg, Ser. VII., Tom. XI., No. 6.
 
("'"><') A. Krohn. "Beobacht. a. d. Entwick. d. Holothurien u. Seeigel."
M tiller's Archiv, 1851.
 
(Vi7) A. Krohn. " Ueb. d. Entwick. d. Seesterne u. Holothurien." Muller's
Ardiir,
 
A. Krohn. "Beobacht. lib. Echinodermenlarven." Miiller's Archiv,
18(4.
 
('>'>'.)} II. Ludwig. "Ueb. d. primar. Steinkanal d. Crinoideen, nebst vergl.
anat. Bemerk. ub. d. Echinodermen." Zeit.f. wiss. Zoo/., Vol. xxxiv. iSSo.
 
(">r,n) K. Metschnikoff. "Studien lib. d. Entwick. d. Echinodermen u.
Nemertinen." Mem. .!< . J', : /i'rsfa>nr?. Scries VII., Tom. XIV., No. 8. 1869.
 
(501)' Joh. Miillcr. " Ueb. d. Larven u. d. Metamorphose d. EchinodcM men.'
Alhandlnng,-n d. />>///'. Akad. (Five Memoirs), 1848, 49, 50. 52 (two Mnnoirs).
 
Joh. Miiller. " Allgemeincr Plan d. Entwicklung d. Echinodermen.
Abhandl. d. Berlin. Akad., 1853.
 
1 The dates in this reference are the dates of publication.
 
 
 
BIBLIOGRAPHY. xxiil
 
 
 
(563). E. Selenka. "Zur Entwicklung d. Holothurien." Ztit. f. wiss. Zoo/.,
Ed. xxvn. 1876.
 
(564) E. Selenka. "Keimblatter u. Organanlage bei Echiniden." Zeit.f.wiss.
Zool.t Vol. xxxni. 1879.
 
(565) Sir Wyville Thomson. " On the Embryology of the Echinodcrmata."
Natural History Review, 1864.
 
(566) Sir Wyville Thomson. "On the Embryogeny of Antedon rosacetw."
Phil. Trans. 1865.
 
ENTEROPNEUSTA.
 
(567) A. Agassiz. "Tornaria." Ann. Lyceum Nat. Hist. vin. New York,
1866.
 
(568) A. Agassiz. "The History of Balanoglossus and Tornaria." Mem.
Amer. Acad. of Arts and Scien., Vol. IX. 1873.
 
(569) A. Gotte. " Entwicklungsgeschichte d. Comatula Mediterranea. " Archiv
fur mikr. Anat., Bd. XII., 1876, p. 641.
 
(570) E. Metschnikoff. " Untersuchungen lib. d. Metamorphose, etc. (Tornaria)." Zeit.fiir wiss. Zool., Bd. XX. 1870.
 
(571) J. M tiller. " Ueb. d. Larven u. Metamor. d. Echinodermen." Berlin.
Akad., 1849 and 1850.
 
(572) J. W. Spengel. "Bau u. Entwicklung von Balanoglossus." Tagebl.d.
Naturf. Vers. Mtinchen, 1877.
 
 
 
CAMBRIDGE : PRINTKD BY C. J. CLAY, M.A. & SON, AT THE UNIVERSITY PRtSS.
 
 
 
 
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Foster M. and Sedgwick A. The Works of Francis Balfour Vol. II. A Treatise on Comparative Embryology 1. (1885) MacMillan and Co., London.

The Ovum and Spermatozoon | The Maturation and Impregnation of the Ovum | The Segmentation of the Ovum | Dicyemae and Orthonectidae Dicyema | Porifera | Coelenterata | Platyhelminthes | Rotifera | Mollusca | Polyzoa | Brachiopoda | Chilopoda | Discophora | Gephyrea | Chaetognatha | Nemathelminthes | Tracheata | Crustacea | Pcecilopoda | Echinodermata | Enteropneusta | Bibliography
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This historic 1885 book edited by Foster and Sedgwick is the second of Francis Balfour's collected works published in four editions. Francis (Frank) Maitland Balfour, known as F. M. Balfour, (November 10, 1851 - July 19, 1882) was a British biologist who co-authored embryology textbooks.



The Works of Francis Balfour Foster M. and Sedgwick A. The Works of Francis Balfour Vol. I. Separate Memoirs (1885) MacMillan and Co., London.

Foster M. and Sedgwick A. The Works of Francis Balfour Vol. II. A Treatise on Comparative Embryology 1. (1885) MacMillan and Co., London.

Foster M. and Sedgwick A. The Works of Francis Balfour Vol. III. A Treatise on Comparative Embryology 2 (1885) MacMillan and Co., London.

Foster M. and Sedgwick A. The Works of Francis Balfour Vol. IV. Plates (1885) MacMillan and Co., London.

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Vol II. A Treatise on Comparative Embryology (1885)

CHAPTER XIX. PCECILOPODA, PYCNOGONIDA, TARDIGRADA, AND LINGUATULIDA; AND COMPARATIVE SUMMARY OF ARTHROPODAN DEVELOPMENT

THE groups dealt with in the present Chapter undoubtedly belong to the Arthropoda. They are not closely related, and in the case of each group it is still uncertain with which of the main phyla they should be united. It is possible that they may all be offshoots from the Arachnidan phylum.

PCECILOPODA.

The development of Limulus has been studied by Dohrn (No. 533) and Packard (No. 534). The ova are laid in the sand near the spring-tide marks. They are enveloped in a thick chorion formed of several layers ; and (during the later stages of development at any rate) there is a membrane within the chorion which exhibits clear indications of cell outlines 1 .

There is a centrolecithal segmentation, which ends in the formation of a blastoderm enclosing a central yolk mass. A ventral plate is then formed, which is thicker in the region where the abdomen is eventually developed. Six segments soon become faintly indicated in the cephalothoracic region, the ends of which grow out into prominent appendages (fig. 245 A) ; of these there are six pairs, which increase in size from before backwards. A stomodaeum (m) is by this time established and is placed well in front of the foremost pair of appendages'*-.

In the course of the next few days the two first appendages of the abdominal region become formed (vide fig. 245 C shewing those abdominal appendages at a later stage), and have a very different shape and direction to those of the cephalothorax. The appendages of the latter become

1 The nature of the inner membrane is obscure. It is believed by Packard to be moulted after the formation of the limbs, and to be equivalent to the amnion of Insects, while by Dohrn it is regarded as a product of the follicle cells.

2 Dohrn finds at first only five appendages, but thinks that the sixth (the anterior one) may have been present but invisible.


PCECILOPODA.


535


flexed in the middle in such a way that their ends become directed towards the median line (fig. 245 B). The body of the embryo (fig. 245 B) is now distinctly divided into two regions the cephalothoracic in front, and the abdominal behind, both divided into segments.



FIG. 245. THREE STAGES IN THE DEVELOPMENT OF LIMULUS POLYPHEMUS. (Somewhat modified from Packard.)

A. Embryo in which the thoracic limbs and mouth have become developed on the ventral plate. The outer line represents what Packard believes to be the amnion.

B. Later embryo from the ventral surface.

C. Later embryo, just before the splitting of the chorion from the side. The full number of segments of the abdomen, and three abdominal appendages, have become established ; m. mouth ; I IX. appendages.

Round the edge of the ventral plate there is a distinct ridge the rudiment of the cephalothoracic shield.

With the further growth of the embryo the chorion becomes split and cast off, the embryo being left enclosed within the inner membrane. The embryo has a decided ventral flexure, and the abdominal region grows greatly and forms a kind of cap at the hinder end, while its vaulted dorsal side becomes divided into segments (fig. 245 C). Of these there are according to Dohrn seven, but according to Packard nine, of which the last forms the rudiment of the caudal spine.

In the thoracic region the nervous system is by this stage formed as a ganglionated cord (Dohrn), with no resemblance to the peculiar cesophageal ring of the adult. The mouth is stated by Dohrn to lie between the second pair of limbs, so that, if the descriptions we have are correct, it must have by this stage changed its position with reference to the appendages. Between the thorax and abdomen two papillae have arisen which form the


536


PCEC1LOPODA.


so-called lower lip of the adult, but from their position and late development they can hardly be regarded as segmental appendages. In the course of further changes all the parts become more distinct, while the membrane in which the larva is placed becomes enormously distended (fig. 246 A). The rudiments of the compound eyes are formed on the third (Packard) or fourth (Dohrn) segment of the cephalothorax, and the simple eyes near the median line in front. The rudiments of the inner process of the chelae of the cephalothoracic appendages arise as buds. The abdominal appendages become more plate-like, and the rudiments of a third pair appear behind the two already present. The heart appears on the dorsal surface.

An ecdysis now takes place, and in the stage following the limbs have approached far more closely to their adult state (fig. 246 A). The cephalothoracic appendages become fully jointed ; the two anterior abdominal appendages (vn.) have approached, and begin to resemble the oper


ce.



VIII


FlO. 246. TWO STAGES IN THE DEVELOPMENT OF LlMULUS POLYPHEMUS.

(After Dohrn.)

A. An advanced embryo enveloped in the distended inner membrane shortly before hatching ; from the ventral side.

B. A later embryo at the Trilobite stage, from the dorsal side. I., vii., VIII. First, seventh, and eight appendages.

cs. caudal spine ; se. simple eye ; ce. compound eye.

culum of the adult, and on the second pair is formed a small inner ramus. The segmentation of the now vaulted cephalothorax becomes less obvious, though still indicated by the arrangement of the yolk masses which form the future hepatic diverticula.

Shortly after this stage the embryo is hatched, and at about the time of hatching acquires a form (fig. 246 B) in which it bears, as pointed out by Dohrn and Packard, the most striking resemblance to a Trilobite.

Viewed from the dorsal surface (fig. 246 B) it is divided into two distinct regions, the cephalothoracic in front and the abdominal behind. The cephalothoracic has become much flatter and wider, has lost all trace of its previous segmentation, and has become distinctly trilobed. The


PCECILOPODA. 537


central lobe forms a well-marked keel, and at the line of insertion of the rim-like edge of the lateral lobes are placed the two pairs of eyes (se and ce). The abdominal region is also distinctly trilobed and divided into nine segments ; the last, which is merely formed of a median process, being the rudiment of the caudal spine. The edges of the second to the seventh are armed with a spine. The changes in the appendages are not very considerable. The anterior pair nearly meet in the middle line in front or the mouth ; and the latter structure is completely covered by an upper lip. Each abdominal appendage of the second pair is provided with four gill-lamellas, attached close to its base.

Three weeks after hatching an ecdysis takes place, and the larva passes from a trilobite into a limuloid form. The segmentation of the abdomen has become much less obvious, and this part of the embryo closely resembles its permanent form. The caudal spine is longer, but is still relatively short. A fourth pair of abdominal appendages is established, and the first pair have partially coalesced, while the second and third pairs have become jointed, their outer ramus containing four and their inner three joints. Additional gill-lamellae attached to the two basal joints of the second and third abdominal appendages have appeared.

The further changes are not of great importance. They are effected in a series of successive moults. The young larvae swim actively at the surface.

Our, in many respects, imperfect knowledge of the development of Limulus is not sufficient to shew whether it is more closely related to the Crustacea or to the Arachnida, or is an independent phylum.

The somewhat Crustacean character of biramous abdominal feet, etc. is not to be denied, but at the same time the characters of the embryo appear to me to be decidedly more arachnidan than crustacean. The embryo, when the appendages are first formed, has a decidedly arachnidan facies. It will be remembered that when the limbs are first formed they are all post-oral. They resemble in this respect the limbs of the Arachnida, and it seems to be probable that the anterior pair is equivalent to the cheliceras of Arachnida, which, as shewn in a previous section, are really post-oral appendages in no way homologous with antennae 1 .

The six thoracic appendages may thus be compared with the six Arachnidan appendages; which they resemble in their relation to the mouth, their basal cutting blades, etc.

The existence of abdominal appendages behind the six cephalothoracic does not militate against the Arachnidan affinities of Limulus, because in the Arachnida rudimentary abdominal appendages are always present in the embryo. The character of the abdominal appendages is probably

1 Dohrn believes that he has succeeded in shewing that the first pair of appendages of Limulus is innervated in the embryo from the supra-cesophageal ganglia. His observations do not appear to me conclusive, and, arguing from what we know of the development of the Arachnida, the innervation of these appendages in the adult can be of no morphological importance.


538 PYCNOGONIDA.


secondarily adapted to an aquatic respiration, since it is likely (for the reasons already mentioned in connection with the Tracheata) that if Limulus has any affinities with the stock of the Tracheata it is descended from airbreathing forms, and has acquired its aquatic mode of respiration. The anastomosis of the two halves of the generative glands is an Arachnidan character, and the position of the generative openings in Limulus is more like that in the Scorpion than in Crustacea.

A fuller study of the development would be very likely to throw further light on the affinities of Limulus, and if Packard's view about the nature of the inner egg membrane were to be confirmed, strong evidence would thereby be produced in favour of the Arachnidan affinities.

(533) A. Dohrn. "Untersuch. Ub. Bau u. Entwick. d. Arthropoden (Limulus polyphemus)." Jenaische Zeitschrift, Vol. vi., 1871.

(534) A. S. Packard. "The development of Limulus polyphemus." Mem. Boston Soc. Nat. History, Vol. II., 1872.

PYCNOGONIDA.

The embryos, during the first phases of their development, are always carried by the male in sacks which are attached to a pair of appendages (the third) specially formed for this purpose. The segmentation of the ovum is complete, and there is in most forms developed within the eggshell a larva with three pairs of two-jointed appendages, and a rostrum placed between the front pair.

It will be convenient to take Achelia kevis, studied by Dohrn (No. 536), as type.

The larva of Achelia when hatched is provided with the typical three pairs of appendages. The foremost of them is chelate, and the two following pairs are each provided with a claw. Of the three pairs of larvalappendages Dohrn states that he has satisfied himself that the anterior is innervated by the supra-cesophageal ganglion, and the two posterior by separate nerves coming from two imperfectly united ventral ganglia. The larva is provided with a median eye formed of two coalesced pigment spots, and with a simple stomach.

The gradual conversion of the larva into the adult takes place by the elongation of the posterior end of the body into a papilla, and the formation there, at a later period, of the anus ; while at the two sides of the anal papilla rudiments of a fresh pair of appendages the first pair of ambulatory limbs of the adult make their appearance. The three remaining pairs of limbs become formed successively as lateral outgrowths, and their development is accomplished in a number of successive ecdyses. As they are formed caeca from the stomach become prolonged into them. For each of them there appears a special ganglion. While the above changes are taking place the three pairs of larval appendages undergo considerable reduction. The anterior pair singly becomes smaller, the second loses its claw, and the third becomes reduced to a mere stump. In the adult the


PENTASTOMIDA. 539


second pair of appendages becomes enlarged again and forms the so-called palpi, while the third pair develops in the male into the egg-carrying appendages, but is aborted in the female. The first pair form appendages lying parallel to the rostrum, which are sometimes called pedipalpi and sometimes antennae.

The anal papilla is a rudimentary abdomen, and, as Dohrn has shewn, contains rudiments of two pairs of ganglia.

The larvae of Phoxichilidium are parasitic in various Hydrozoa (Hydractinia, etc.). After hatching they crawl into the Hydractinia stock. They are at first provided with the three normal pairs of larval appendages. The two hinder of these are soon thrown off, and the posterior part of the trunk, with the four ambulatory appendages belonging to it, becomes gradually developed in a series of moults. The legs, with the exception of the hindermost pair, are fully formed at the first ecdysis after the larva has become free. In the genus Pallene the metamorphosis is abbreviated, and the' young are hatched with the full complement of appendages.

The position of the Pycnogonida is not as yet satisfactorily settled. The six-legged larva has none of the characteristic features of the Nauplius, except the possession of the same number of appendages.

The number of appendages (7) of the Pycnogonida does not coincide with that of the Arachnida. On the other hand, the presence of chelate appendages innervated in the adult by the supra-cesophageal ganglia rather points to a common phylum for the Pycnogonida and Arachnida ; though as shewn above (p. 455) all the appendages in the embryo of true Arachnida are innervated by post-oral ganglia. The innervation of these appendages in . the larvae of Pycnogonida requires further investigation. Against such a relationship the extra pair of appendages in the Pycnogonida is no argument, since the embryos of most Arachnida are provided with four such extra pairs. The two groups must no doubt have diverged very early.

BIBLIOGRAPHY.

(535) G. Cavanna. " Studie e ricerche sui Picnogonidi." Pubblicazioni del R. Institute di Studi stiperiori in Firenze, 1877.

(536) An. Dohrn. " Ueber Entwickhuig u. Baud. Pycnogoniden." Jenaische Zeitschrift, Vol. v. 1870, and " Neue Untersuchungen lib. Pycnogoniden." Mitthdl. a. d. zoologischen Station zu Neafel, Bd. I. 1878.

(537) G. Hodge. " Observations on a species of Pycnogon, etc." Annal. and Mag. of Nat. Hist. Vol. ix. 1862.

(538) C. Semper. " Ueber Pycnogoniden u. ihre in Hydroiden schmarotzenden Larvenformen." Arbeiten a. d. zool.-zoot. Instit. Wiirzburg, Vol. I. 1874.

PENTASTOMIDA.

The development and metamorphosis of Pentastomum taenoides have been thoroughly worked out by Leuckart (No. 540) and will serve as type for the group.


540 PENTASTOMIDA.


In the sexual state it inhabits the nasal cavities of the dog. The early embryonic development takes place as the ovum gradually passes down the uterus. The segmentation appears to be complete ; and gives rise to an oval mass in which the separate cells can hardly be distinguished. This gradually differentiates itself into a characteristic embryo, divided into a tail and trunk. The tail is applied to the ventral surface of the trunk, and on the latter two pairs of stump-like unsegmented appendages arise, each provided with a pair of claws. At the anterior extremity of the body is formed the mouth, with a ventral spine and lateral hook, which are perhaps degenerated jaws. The spine functions as a boring apparatus, and an apparatus with a similar function is formed at the end of the tail. A larval cuticle now appears, which soon becomes detached from the embryo, except on the dorsal surface, where it remains firmly united to a peculiar papilla. This papilla becomes eventually divided into two parts, one of which remains attached to the cuticle, while the part connected with the embryo forms a raised cross placed in a cup- shaped groove. The whole structure has been compared, on insufficient grounds, to the dorsal organ of the Crustacea.

The eggs, containing the embryo in the condition above described, are eventually carried out with the nasal slime, and, if transported thence into the alimentary cavity of a rabbit or hare, the embryos become hatched by the action of the gastric juice. From the alimentary tract of their new host they make their way into the lungs or liver. They here become enveloped in a cyst, in the interior of which they undergo a very remarkable metamorphosis. They are, however, so minute and delicate that Leuckart was unable to elucidate their structure till eight weeks after they had been swallowed. At this period they are irregularly-shaped organisms, with a most distant resemblance to the earlier embryos. They are without their previous appendages, but the alimentary tract is now distinctly differentiated. The remains of two cuticles in the cyst seem to shew that the above changes are effected in two ecdyses.

In the course of a series of ecdyses the various organs of the larval form known as Pentastomum denticulatum continue to become differentiated. After the first (= third) ecdysis the cesophageal nerve-ring and sexually undifferentiated generative organs are developed. At the fourth (=sixth) ecdysis the two pairs of hooks of the adult are formed in pockets which appeared at a somewhat earlier stage ; and the body acquires an annulated character. At a somewhat earlier period rudiments of the external generative organs indicate the sex of the larva.

After a number of further ecdyses, which are completed in about six months after the introduction of the embryos into the intermediate host, the larva attains its full development, and acquires a form in which it has long been known as Pentastomum denticulatum. It now leaves its cyst and begins to move about. It is in a state fit to be introduced into its final host ; but if it be not so introduced it may become encysted afresh.

If the part of a rabbit or hare infected by a Pentastomum denticulatum be eaten by a dog or wolf, the parasite passes into the nasal cavity of the


TARDIGRADA. 541


latter, and after further changes of cuticle becomes a fully-developed sexual Pentastomum taenioides, which does not differ to any very marked extent from P. denticulatum.

In their general characters the larval migrations of Pentastomum are similar to those of the Cestodes.

The internal anatomy of the adult Pentastomum, as well as the characters of the larva with two pairs of clawed appendages, are perhaps sufficient to warrant us in placing it with the Arthropoda, though it would be difficult to shew that it ought not to be placed with such a form as Myzostomum (vide p. 369). There do not appear to be any sufficient grounds to justify its being placed with the Mites amongst the Arachnida. If indeed the rings of the body of the Pentastomida are to be taken as implying a true segmentation, it is clear that the Pentastomida cannot be associated with the Mites.

BIBLIOGRAPHY.

(539) P. J. van Beneden. " Recherches s. 1'organisation et le developpement d. Linguatules." Ann. d. Sden. Nat., 3 Ser., Vol. XI.

(540) R. Leuckart. " Bau u. Entwicklungsgeschichte d. Pentastomen." Leipzig and Heidelberg. 1860.

TARDIGRADA.

Very little is known with reference to the development of the Tardigrada. A complete and regular segmentation (von Siebold, Kaufmann, No. 541) is followed by the appearance of a groove on the ventral side indicating a ventral flexure. At about the time of the appearance of the groove the cells become divided into an epiblastic investing layer and a central hypoblastic mass.

The armature of the pharynx is formed very early at the anterior extremity, and the limbs arise in succession from before backwards.

The above imperfect details throw no light on the systematic position of this group.

Tardigrada.

(541) J. Kaufmann. " Ueber die Entwicklung u. systematische Stellung d. Tardigraden." Zeit.f. wiss, ZooL, Bd. HI. 1851.

Summary of Arthropodan Development. The numerous characters common to the whole of the Arthropoda led naturalists to unite them in a common phylum, but the later researches on the genealogy of the Tracheata and Crustacea tend to throw doubts on this conclusion, while there is not as yet sufficient evidence to assign with certainty a definite position in either of these classes to the smaller groups described in the present chapter. There seems to be but little


542 SUMMARY.


doubt that the Tracheata are descended from a terrestrial Annelidan type related to Peripatus. The affinities of Peripatus to the Tracheata are, as pointed out in a previous chapter (p. 386), very clear, while at the same time it is not possible to regard Peripatus simply as a degraded Tracheate, owing to the fact that it is provided with such distinctly Annelidan organs as nephridia, and that its geographical distribution shews it to be a very ancient form.

The Crustacea on the other hand are clearly descended from a Phyllopod-like ancestor, which can be in no way related to Peripatus.

The somewhat unexpected conclusion that the Arthropoda have a double phylum is on the whole borne out by the anatomy of the two groups. Without attempting to prove this in detail, it may be pointed out that the Crustacean appendages are typically biramous, while those of the Tracheata are never at any stage of development biramous 1 ; and the similarity between the appendages of some of the higher Crustacea and those of many Tracheata is an adaptive one, and could in no case be used as an argument for the affinity of the two groups.

The similarity of many organs is to be explained by both groups being descendants of Annelidan ancestors. The similarity of the compound eye in the two groups cannot however be explained in this way, and is one of the greatest difficulties of the above view. It is moreover remarkable that the eye of Peripatus 2 is formed on a different type to either the single or compound eyes of most Arthropoda.

The conclusion that the Crustacea and Tracheata belong to two distinct phyla is confirmed by a consideration of their development. They have no doubt in common a centrolecithal segmentation, but, as already insisted on, the segmentation is no safe guide to the affinities.

In the Tracheata the archenteron is never, so far as we know, formed by an invagination 3 , while in Crustacea the

1 The biflagellate antennae of Pauropus amongst the Myriapocls can hardly be considered as constituting an exception to this rule.

3 I hope to shew this in a paper I am preparing on the anatomy of Peripatus.

8 Stecker's description of an invagination in the Chilognatha cannot be accepted without further confirmation ; -vide p. 388.


SUMMARY. 543


evidence is in favour of such an invagination being the usual, and, without doubt, the primitive, mode of origin.

The mesoblast in the Tracheata is formed in connection with a median thickening of the ventral plate. The unpaired plate of mesoblast so formed becomes divided into two bands, one on each side of the middle line.

In both Spiders and Myriopods, and probably Insects, the two plates of mesoblast are subsequently divided into somites, the lumen of which is continued into the limbs.

In Crustacea the mesoblast usually originates from the walls of the invagination, which gives rise to the mesenteron.

It does not become divided into two distinct bands, but forms a layer of scattered cells between the epiblast and hypoblast, and does not usually break up into somites ; and though somites are stated in some cases to be found they do not resemble those in the Tracheata.

The proctodaeum is usually formed in Crustacea before and rarely later 1 than the stomodaeum. The reverse is true for the Tracheata. In Crustacea the proctodseum and stomodaeum, especially the former, are very long, and usually give rise to the greater part of the alimentary tract, while the mesenteron is usually short.

In the Tracheata the mesenteron is always considerable, and the proctodaeum is always short. The derivation of the Malpighian bodies from the proctodaeum is common to most Tracheata. Such diverticula of the proctodaeum are not found in Crustacea.

1 This is stated to be the case in Moina (Grobben).

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