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Jenkinson JW. Experimental Embryology. (1909) Claredon Press, Oxford.

Jenkinson (1909): 1 Introductory | 2 Cell-Division and Growth | 3 External Factors | 4 Internal Factors | 5 Driesch’s Theories - General Conclusions | 6 Appendices
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Appendix A

Further Remarks on Relation Between the Symmetry of the Egg, The Symmetry of Segmentation, and the Symmetry of the Embryo in the Frog

IN the measurements, referred to above (pp. 165-8), of the angles between the plane of symmetry of the egg (as determined by the position of the grey crescent), the first furrow and the sagittal plane of the embryo, it was found (1) that there was a certain tendency for the first furrow and the sagittal plane to coincide, since in a. large number of cases small angles preponderated over large ones, the standard deviation of this angle from the mean (which was practically = 0°) being a- = 40-39° i-65 ; (2) that there was a much greater tendency for the plane of symmetry and the sagittal plane to coincide, the standard deviation of the angle between these two planes being o'=29-75° _-J; -63 ; (3) that the first furrow tended either to coincide with or to lie at right angles to the plane of symmetry, the standard deviation about 0° being 18-70° i -60, that about 90° being 23-29° j-_ -86, the value of 0' for all the observations being 47-90° 1- 1-19. The correlation between the first furrow and the sagittal plane was found to be p=-138i -031, that between the plane of symmetry

and the sagittal plane p=-372i -025, that between the plane of symmetry and the first furrow p=-O87 i -032.

These results may be tabulated as follows : rr :0 40-39° + -65. -138 i -031.

tal Plane.

Plane of Symmetry and Sagittal Plane. l 2975 -t '63’

Plane of Symmetry and First Furrow.

First Furrow and Sagit- }

.372 i .025.

} 47.9oi1.19. .os7¢_.o32.

Full details of these results will be found in a paper in Biometrika V. 1906.

For the purpose of making these measurements the eggs were placed in rows parallel to the [mat]; of glass slides, and the angles measured between the various planes and lines ruled across the slide. Such eggs compress one another by their jelly coats; further, the eggs taken ‘from the uterus were placed haphazard on the slides with the axis making any direction with the vertical. The egg takes about half-an-hour to turn into its normal position with the axis vertical, and during this interval gravity may possibly act upon the yolk and protoplasm, of different specific gravities, and impress a plane of bilateral gravitation symmetry upon the egg, as occurs when the egg is permanently inverted (see above, pp. 82-87). This obliquity of the axis may possibly afiect the relations between the planes, and the mutual compression may also be a disturbing factor, since it is known that in compressed eggs the nuclear spindle is perpendicular to the direction of the pressure (pp. 34-36).

These angles have therefore now been measured under four different conditions:

(a) The eggs are close to one another in the rows and the axis is horizontal.‘ (Since the rows are parallel to the length of the slide the pressure, if any, must be in the same direction, while the surfaces of compression or contact are across the slide. The eggs were always so placed that the vegetative poles faced in one direction and the planes of ‘ gravitation symmetry ’ were at right angles to the length of the slide. This holds good of all the following experiments.)

(/3) The eggs close, but the. axis vertical with the white pole below. In these there can be no gravitation plane of symmetry.

(y) The eggs spaced, but the axis horizontal. In these the jellies do not touch.

(6) The eggs spaced and the axis vertical. In these, therefore, both the supposedly disturbing factors are removed. The results are given in the following table :—


First Furrow and Plane of Symmetry Plane of Symmetry Sagittal Plane. and Sagittal Plane. and First Furrow.

(.7) .7 = 38-42 g._ -70. .7 = 31-86: -56. .7 = 41-591-_-84. ,7 = -201;-028. ,7 = -263;:-_-027. ,7 -= -118;-029. (.9) .7 = 33-443-_-56. .7 = 30-17:51. .7 = 39-7l_-1;-61. ,7 = 3523-021. .7 = .27si.o22. ,7 = .o23¢.o24. (-,) .7 —_- 33-49;:-_-96. .7 = 27-53¢-84. .7 = 36-60: 1-108. ,. = .292:-039. —_— -399:-036. p = .075:-043. (a) .7 = 31.45133. .7 —_— 26-80¢-82. .7 = 34-46:1-065. ,7 —_- -364:-033. ,7 = -451 1.035. ,7 -_- -186;-043.

It is evident from this that gravity and ‘ mutual compression ’ (as I will for the moment term it, though it is doubtful whether the pressure has anything at all to do with the result) do affect the

magnitude of the angles between these three planes, for in each case the standard deviation falls, while the correlation coeflicient rises, when they are both removed. It will be observed that, while gravitation (y) has less eflect than compression (3) upon the angles B and C, the reverse is the case with the angle A. We may be able to find a reason for this later on.

There is one point worth noticing. It is quite clear that gravity is not indispensable for the development of a grey crescent and plane of symmetry, though it is true that the position of this plane may be aifected by gravity even in the short interval that elapses before the egg turns over.

The values for the compressed eggs with horizontal axes (or) compare fairly well with those previously obtained, except in the case of the plane of symmetry and the first furrow. In the former series the latter tended either to coincide with or to lie at right angles to the former. In the present series this is not the case. This diflerence is probably to be attributed to the fact that many of the eggs in the first series must have been placed on the slide with the white pole upwards: possibly also the ‘ compression ’ was greater then than now.

It is fortunate that the same data enable us to study exactly the relation between the first furrow and the plane of symmetry on the one hand, and the direction of ‘compression’ and of the gravitation symmetry plane on the other. It must be remembered that these two are at right angles to one another.

Consider first the first furrow.

(a) When the eggs are close but the axis horizontal the first furrow tends to lie at right angles to the slide, that is, in the direction of compression, but at right angles to the gravitation symmetry plane. (a-=38-16 i -69.)

(fl) When the eggs are close but the axis vertical this tendency is not quite so marked. (a'=46-67 i -7' 1.)

(y) When the eggs are spaced and the axis horizontal it is still there, but slight. (o-=49-32 ;l-_ 1-40.)

(6) When the eggs are spaced and the axis vertical the direction of the first furrow is random. (zr=52-76¢ 1-17.)

VVe may conclude, therefore, that the first furrow tends to lie in the direction of the ‘ compression’ and at right angles to the plane of gravitation symmetry. The latter tendency, we know, exists in forcibly inverted eggs, together with a tendency to lie in the plane of symmetry and at 45° to it (above, p. 84). Pressure experiments alo show that division is in the direction of pressure (p. 34 sqq.).

The direction taken up by the plane of symmetry under these different circumstances is-quite distinct from that of the first furrow. It appears to be determined in the first instance by gravitation, as it usually lies in the gravitation symmetry plane. It is not, however, only so determined, for if the eggs (compressed and with axi horizontal) be allowed to develop in the light the plane of symmetry lies either in the gravitation symmetry plane, or in the direction of the incident light (parallel to the length of the slide in the experiment , while in the dark it lies only across the slide. That this secon effect is due to the light and not to the pressure is shown by the fact that it occurs when the eggs are spaced, and that it may be made to vary in position by varying the position of the slide with regard to the light. Light, therefore (ordinary daylight), as well as gravity, can help to determine the -position of the plane of symmetry, and when the latter is excluded it appears that this plane is placed either in or at right angles to the source of light.

Light appears to exert no effect u on the first furrow.

It is now intelligible why, when 1 these factors are operative, the relation between the first furrow and the planes of symmetry of egg and embryo should be disturbed, since, in the conditions of the experiment, those factors which determine the position of the former are at right angles to those on which the direction of the latter depends.

It still remains for us to inquire into the internal causes of the direction of these planes in the egg. Roux, as has been pointed out, has asserted that the grey crescent appears on the opposite side of the egg to that on which the spermatozoon has entered (pp. 80, 165), and further that the point of entry of the sperm also determines the meridian of the first furrow, since this either includes the sperm-path, or is parallel to it, or, when it is crooked, includes or is parallel to the inner portion or ‘ copulation ’ path, which is taken to represent the line of approximation of the two pronuclei; the outer part being simply the ‘ penetration’ path. Roux also arbitrarily selected a fertilization meridian (meridian of the sperm-entry), and showed that this became the ventral side (opposite the grey crescent) later on, as well as the ineridian of the first furrow (p. 248).

I have been able to accurately investigate—by means of sections-—the relation between the fertilization meridian, first furrow, and sperm-path in a number of eggs in which the direction of the symmetry plane had been previously determined, and the results of the measurements of these angles are given here. The eggs fall into two series, those which were compressed and had their axes horizontal (a), and those which were spaced and had their axes vertical, the white pole being below (6). In (a) the gravitation symmetry plane and the direction of compression were at right angles to one another, as before.

8 a Meridian of sperm entry a- = 21-02° 1-_ 1-63. o- = 31-04°: 1-34. and first furrow. p = -435 3 -074. 9 =-613 i -038.

Meridian of sperm entry 0' = 25-67° i 1-35. 0 = 41-01° 3-_ 1-78. and symmetry plane. p = -302 i -083. / P = -006 1 -061.

SP§;§§f:;l3(g;§‘}ff1,§§;“ } . .. .—. 17.94° : 1.15. o‘ = 21.47° 1 -93.

From this it is clear that there is a very close relation indeed between the point of entry of the spermatozoon and the direction of the first furrow, especially when the disturbing efiects of pressure and gravity are removed. There is, however, little relation between the sperm meridian and the plane of symmetry even under the most favourable circumstances, and when the conditiofis are not favourable the correlation is negligible. There is however (in the 6 series) a considerable correlation (p = -479 i '070) between the sperm-pat/l and the plane of symmetry. It should be remembered, however, that all these eggs were exposed to the light. From what we know of the eifect of this agent upon the direction of the symmetry plane, it would not perhaps be too hold a hazard to surmise that in darkness there would be a correlation between the sperm entrance and the plane of symmetr .

Eiien after the removal of this disturbance there remain factors which interfere with the completeness of the correlation between these planes; these must probably be looked for in the incomplete radial symmetry of certain eggs—due possibly to pressure in the uterus—and to the slight squeezings and distortions the eggs may be subjected to when they are being taken from the Frog.

It will be seen that the relation between the sperm-path and first furrow is closer than that between the latter and the sperm entrance. This is because though the furrow may be placed to one side of the entrance point, it may still be parallel to the path , or, if not to the ‘penetration ’ path then to the inner or ‘copulation ’ path, as observed by Roux. This ‘ copulation’ path is usually observed when the penetration path is turned away from the first furrow, that i, when it has not been directed towards the egg-axis.

The same data give the position of the point or of entrance with regard to the direction of ‘pressure ’ and ‘gravitation symmetry’. In the (a) series the sperm tends to enter in the direction of ‘pressure’, that is, on that side of the egg on which it is in contact with its neighbours. Hardly a single spermatozoon enters on that side of the egg on which the white pole had been turned up, and very few on the opposite side.

It is scarcely possible to suppose that either the compression of the egg or the gravitation plane brings the spermatozoa round to the side of compression, but it may be imagined that either by capillarity or by some chemotactic stimulus the spermatozoa are especially attracted to the point where the rapidly swelling coats of adjacent eggs come into contact, and that therefore fertilization is principally effected upon this side. This explains why the first furrow lies so often in this direction. The pressure may of course afiect the position of the planes in the egg later on.

When the eggs are spaced the sperm enters on any side at random. The deviation of the sperm entrance from the egg-axis (the angle between sperm-entrance radius and egg-axis) varies in the two series of observations. When the eggs are spaced and the axes vertical, the sperm enters mainly near the equator, never near the animal pole; when the eggs are compressed and the axis horizontal, usually at about 45° from the axis, though it may enter near the pole or near the equator. This difierence obviously depends on the diiference in the initial position of the eggs on the slide. The deviation has apparently very little effect on any of the planes we have been considering.

Finally, let us try and gain some conception of the mechanism by which the direction of the furrow depends on the point of sperm entry. It is apparently quite simple, for the sperm-path is directed usually towards the axis, the sperm nucleus travels along that path to meet the female nucleus, which is also in the axis, the centrosome of the sperm divides at right angles to that path, the fertilization spindle is developed between the diverging centrosomes and cell-division takes place in the equator of the spindle ; the first furrow includes therefore the sperm-path. Should, however, the ‘penetration ’ path not be exactly radial, for whatever reason, the sperm nucleus turns aside to meet the female pronucleus, there is a ‘ copulation’, as distinct from a ‘ penetration’ path, the centrosome divides at right angles to the former, and this, then, is included in or parallel to the plane of the furrow. In those cases in which the sperm-path is parallel to the furrow it is always quite close to it, and we may suppose perhaps that the first division "has not been quite equal. (The division of the centrosomes has not, I believe, been observed in the Frog, and the foregoing description has been taken from the Axolotl. In this genus the definitive centrosome is formed from the sperm nucleus, when the latter has already penetrated some little way into the egg.) .

The causes of the formation of the grey crescent which marks the symmetry plane are not so clear.

Roux describes it as being due to the immigration of superficial pigment. Now we have strong reason for believing that both the entrance-funnel——produced when the spermatozoon first touches the egg-—and the sperm-sphere are local aggregations of watery substance. The accumulation of what appears to be a more watery substance about the middle piece which has been observed in the Axolotl,appears also to occur in the Frog: at least the same formation of large clear vacuoles in the sperm-sphere may be seen in the latter as in the former. Should this be actually so, we may suppose that the streaming movement centred in the entrance-funnel and sperm-sphere is responsible for drawing away the pigment from a certain region of the surface; hence the grey crescent. The sperm-sphere is on the inner side of the sperm nucleus: hence the grey crescent would appear on that side of the egg which is opposite to the entrance of the spermatozoon, should no disturbance of the streaming movement have taken place, and, since the sperm-path is radial, would be symmetrically disposed with regard to it. In this case, fertilization meridian, sperm-path, grey crescent and plane of symmetry, first furrow, and, later on, sagittal plane, would all coincide. There is, as we have seen, a very fair correlation between the sperm-entrance and the first furrow, and again between the sperm-path and the grey crescent. But should some other streaming movement of the cytoplasm be set up by the gravitation of the heavy yolk particles, or by pressure, or by light, then the relation between the two processes, the division of the centrosome which determines the direction of the first furrow, on the one hand, and on the other, the streaming movement towards the sperm-sphere which determines the position of the grey crescent, would be disturbed, and while the entrance point of the sperm might still continue to determine, though not so completely, the position of the furrow, it might come to be without relation to the symmetry of the egg and of the embryo; and this is what is actually observed.

Though it is diflicult to assign the exact cause of each and every deviation from the rule, this much is certain, that however they may coincide in ‘typical’ development (I use R0ux’s expression), the factors which determine cell-division, and those which determine differentiation, may be influenced by different external causes in widely diifering ways, and are therefore presumably distinct. Nor does this artificial separation of the two processes in any wise prejudice the complete normality of the development of the embryo".

Lillie has shown (Jozmz. Esp. Z002. iii. 1906) that in the egg of C’/Iaetopterus there are granules of difierent kinds which pass, in segmentation, into definite cells. By means of the centrifuge some of these--the endoplasmic—-may be driven to one side of the egg, but in whatever position these organ-forming granules may be thus artificially placed, the cleavage has the same relation to the egg axis (as determined by the polar bodies) as in the normal egg. The factors of cell-division are thus separable from those of differentiation.

To the cases quoted in the summary on pp. 245, 246 might be added the various instances in which an egg may be made, by heat or pressure or shaking, or in artificial parthenogenesis, to segment abnormally and yet give rise to a normal larva.

Appendix B

On the Part Played by the Nucleus in Differentiation

(i) BOVERI has more recently (Zellen-Studim, vi, Jena, 1907) published a very elaborate account of the irregularities produced by dispermy in Echinoid eggs, in which are brought forward

still more facts in proof of the qualitative difference of the chromosomes.

As has been stated above, p. 263, dispermy is induced by the simple expedient of adding a large quantity of sperm to the eggs. The following types of dispermy are distinguished.

A. Tetracentric, i. e. each sperm centre divides. (i) 'I‘etraster, with four spindles.

(ii) Double spindle, i. e. the female and one male pronucleus lie in one spindle, the other male lies aside in its spindle.

B. Tricentric, one sperm centre remaining undivided. (i) Triaster, a tripolar figure with three spindles.

(ii) Monaster-amphiaster, the undivided sperm centre remaining apart with one sperm nucleus.

C. Dicentric, neither sperm centre dividing. (i) Amphiaster, a spindle is formed between the two centres.

(ii) Double monaster: the centres remain apart, one with one male, the other with the other male and the female pronucleus.

The segmentation of these eggs is as follows.

The tetraster divides simultaneously into four, which may either lie in one plane if the divisions are meridional, or be tetrahedrally arranged. In the first case another meridional division ensues, followed by an equatorial, then ‘eight micromeres are formed, eight macromeres, and sixteen mesomeres. In the latter case not more than three cells can share in the micromere region and only four or six of these are produced. The triaster eggs, having divided simultaneously into three (meridionally), subsequently show six micromeres, six macromeres, and twelve mesomeres.

The segmentation of the double spindle eggs is interesting and important. Usually the egg divides across the two spindles into two binucleate cells, but it may divide at once into four, or into three, one of which is binucleate. The interest lies in the binucleate cells, for they continue to produce uni-nucleate and binucleate cells until the latter divide simultaneously into four, and this simultaneous division may sometimes involve an irregular distribution of the chromosomes, with fatal consequences to the cell. Bovcri had already produced evidence of the evil effects of an irregular distribution of the 3 n x 2 chromosomes present in triasters and tetrasters. A more detailed account is now given.

Of the tripartite (triaster) ova about 8 % on an average produced Plutei. In these larvae three regions may be distinguished in the egg by the size of the nuclei (proportional to the number of chromosomes) and the boundaries between them may be shown to correspond to the divisions between the three blastomeres. The form is asymmetrical in skeleton and pigment, but Bovcri shows that both sides are normal, as though the larva had been compounded of two types such as occur, as individual variations, in any culture. It is suggested therefore that the slight differences in the two sides are due to difierences in the two sperms.

Some of the larvae have partial defects in skeleton or pigment, or the skeleton may be much reduced on one side, or one-third of the cells may be pathological, i. e. disintegrate in the segmentation cavity, while the remaining two-thirds are sound and sometimes symmetrical. In this case it is supposed that the degenerate cells had separated from the others at an early stage, and that the remainder had had time to recuperate. In others two-thirds are degenerate, one-third normal, or all three degenerate. When the three blastomeres are isolated and allowed to develop independently, segmentation is partial, with two micromeres, two macromeres, and four mesomeres, and often all three develop normally up to the blastula stage. After that only one or two, rarely all three, become Plutei, the rest giving rise to stereoblastulae or stereogastrulae, full of degenerating cells.

The isolated quarters of tetrasters also segment partially and normally, but few give rise to Plutei. The whole simultaneously quadripartite eggs only rarely give rise to what may be called a Pluteus (2 cases in 1500) ; but very degenerate larvae are found, with masses of disintegrating cells inside, which are assigned to one of the four blastomeres. Stereogastrulae-—with nuclei of all the same size--are frequent.

As has been alread mentioned, Bovcri points out that the probability of each cell’ of a triaster receiving a complete set of the 71. chromosomes of the species when there are 3 n x_2 to be distributed must be greater than‘ that of each cell of tetraster obtaining a full complement, and the probability for one isolated cell must be greater than that for the whole egg. What the mathematical values of these probabilities are Boveri does not know, though he makes an attempt to reckon them—not theoretically, but by means of a mechanical apparatus; the attempt is not quite successful. The fact, however, remains that eight per cent. of the triasters produce normal Plutei, only -06 per cent. of the tetrasters. This does not depend on the cells receiving too much or too little chromatin (see p. 265), nor again on the fact that the ratio between size of nucleus and size of cytoplasm (see pp. 268, 269) can only be satisfied by certain definite numbers of chromosomes, and the only explanation remaining is that for normal development of each and every part the nucleus of each cell must contain a complete set of the specific chrosomomes ; from which it follows that the chromosomes are qualitatively unlike.

A word may be said about the double-spindled eggs (Type A. i). The larvae from these sometimes show abnormal regions, and this is attributed to one or more of the binucleate cells having divided with a tetraster and irregular distribution of chromosomes. Of all such eggs 50 % gave rise to normal Plutei.

The degenerative changes undergone by the nuclei of these larvae are of several types, to be associated again with differences in the combinations of chromosomes.

(ii) Boveri’s experimental proof of the qualitative difference of the chromosomes does not of course of itself involve a belief in the individuality of these bodies, for if the chromatin is concerned in inheritance, it is necessary to suppose that the number of qualitatively distinct bodies is far greater than the number of chromosomes, and these bodies may be differently grouped during each successive resting stage.

The hypothesis of the individuality of the chromosomes, i.e. of a constancy in the manner of grouping of these particles, rests in the first instance on such facts as those observed by Sutton in B2-ac/:3/stola, where in the spermatogonia the chromosomes are of dilferent sizes, which may however be arranged in pairs, together with an odd one or accessory chromosome. 1 In the resting stage the accessory chromosome remains apart in a separate vesicle, while the large chromosomes lie in separate pockets of the nuclear membrane, the small ones, each as a separate reticulum, in the main body of the nucleus. In the spermatocyte a number of bivalent spiremes appear, which show the same dilferences of sizes a the pairs of chromosomes previously, and the accessory chromosome.

The accessory chromosome passes into two only of the four spermatids and is supposed to be a sex-determinant.

Similar facts have been reported by Wilson for several Insects (see Joum. Esp. Zool. ii, iii, 1905, 1906). '

Wilson finds constant size differences between pairs of chromosomes, and either an accessory odd chromosome (which passes into only one half of the germ cells) or a pair of idio-chromosomes of unequal size (one of which goes to one half, the other to the other half of the spermatozoa), or both the accessory and the idio-chromosomes (giving four kinds of spermatozoa). The idiochromosomes are supposed, again, to play a part in sex-determination. Several other observers have found these accessory chromosomes, idio-chromosomes, and pairs of chromosomes of difierent sizes in various Insects (Boring, Journ. E211. Zool. iv. 1907 ; Stevens, ibid. ii. 1905, v. 1908; McClung, Biol. Bull. iii. 1902, ix. 1905; Montgomery, Biol. Bull., vi. 1904; Baumgartner, Biol. Bull. viii. 1904-5 ,- Zweiger, Zool. Anz. xxx. 1906; Nowlin, Jomw. Exp. Zool. iii. 1906); in Spiders (Wallace, Biol. Bull. viii. 1904»-5 ; Berry, Biol. Bull. xi. 1906); and in Myriapods (Blackman, Biol. Bull. v. 1903 ; Medes, Biol. Bull. ix. 1905).

It is a noteworthy fact that the accessory chromosome retains its individuality in the resting stage (looking like a chromatin nucleolus), while the others break up. The belief in the individuality of these others rests therefore on the constancy of the relative sizes from generation to generation.

Further support for the hypothesis may be derived from theoretical speculations. VVe know that only 2; (one-half the normal number) chromosomes are necessary for normal development provided that they comprise a complete set. In sexual reproduction n maternal unite with n paternal. A study of the reducing division shows that 1: whole chromosomes first pair with and are then separated from or whole chromosomes, and that when they dilfer in size those of the same size pair together, and it looks as though paternal were here separated from maternal, though the distribution of paternal and maternal to the two cells will difier, almost certainly, in diiferent cases.

If the particles of which the chromosomes are composed are also to be paired and separated, it would appear to be necessary that their groupin should be constant, in other words that the chromosomes shou d retain their individuality.

(iii) A case of heterogeneous fertilization between eggs of Seaurchins and the sperm of Anletlon has been described above (p. 262). Loeb has recently succeeded in rearing Plutei from the eggs of Slrongylocmlrolue fertilized by the sperm of a Mollusc (0/lloroaloma). Cytological details are not given (Arc/E. Eul. Mecfi. xxvi. 1908). ‘

Index Of Authors

Agassiz: effects of fertilization in Ctenophors, 250.

Aristotle: theory of development, 13.

— the soul in function and development, 292 sqq.

— mechanism and teleology, 296.

Auerbach :' segmentation of Ascuris nigrovenosa, 33.

von Baer, 16.

Balfour: effect of yolk on segmentation, 29, 88.

Bataillon: monstrosities osmotic pressure, 120, 135.

—- artificial parthenogenesis, 124.

Bergh: cell-division in germ-bands of Crustacea, 34.

Berthold: surface-tension and celldivision, 41, 42.

Bischofl‘, 16.

Blane: effect of light upon the development of the Chick, 94, 96.

Boas: rate of growth in man, 63.

— change of variability, 73, 74.

— diminution of correlation coefiicient, 75.

Bonnet : emboitement, 14.

— preformation, 15. Bonnevie : diminution of chromosomes in Ascaris lumbricoidcs, 258. Born : gravity and development, 18, 88-85.

— pressure experiments on Frogs’ eggs, 34, 35.

Boveri : early development of Slrongylocentrotus, 23, 183-185.

— egg of Strongylocentrotus stretched, 39.

— suppression of micromeres in Strongylocentrotus, 186.

-— causes of the pattern of segmentation, 197.

— karyokinetic plane, sperm path,

11 ng first furrow in Strongylocentrotus,

8 .

— potentialities of? animal and vegetative cells, 192.

— stratification of cytoplasmic substances, 242, 280.

-- characters dependent on cytonlmam in Flnhinnid larvae. 261.

due to

Boveri : diminution of chromosomes in Ascaris megalocephala, 252, 255-257.

— due to a difference in the cytoplasm, 257.

— hybrid larva from enucleate egg fragment with characters of male parent, 253, 258-260.

— irregular distribution of chromosomes a cause of abnormality, 253, 263-266.

— individuality of chromosomes and chromatin, 256, 263.

—part played by nucleus in differentiation, 266, 285.

—possiblo significance of reducing divisions, 266.

— number of chromosomes, size of nucleus, and size of cell, 68, 267, 268.

—2méclear division not qualitative,

6 .

Bowditch: rate of growth in man, 63.

-- change of variability, 73.

Brauer : Branchipus, 22, 24.

Brooks: Lucifer, 22.

de Butfon : Preformation, 15.

Bullzt: artificial parthenogenesis, 12 .

Bumpus: change of variability in Litlorina, 71, 72.

Bunge: respiration of Ascaris, 112.

Castle : see Davenpofl: and Castle.

Chabry: segmentation furrows and embryonic axes in Ascidians, 229.

—- development of isolated blastemeres in Ascidians, 229, 230.

Child : critique of Driesch’s vitalism, 292, note.

Chun : isolated blastomeres of Ctenophora, 209.

Conklin: maturation, fertilization, and development of Cynthia, 230236.

— development of isolated blastemeres in Oyntlzia, 237.

— development of pieces of gastrula in Cynthia, 238.

— streaming movements of protonlnsm. 40. 316 INDEX OF

Crampton : isolated blastomeres of Ilycmesaa, 215, 216.

— efieot of removal of the polar lobe, 217.

Dareste: mechanical agitation of the Hen’s egg, 89.

— electricity, 91.

Davenport : catalogue of ontogenetic processes, 4 sqq.

— definition of growth, 58.

— rate of growth, 69.

— the role of water in growth, 58, 59, 115, 116.

- and Castle : acclimatization of eggs of Bufo to heat, 100.

Delage : causes of artificial parthenogenesis, 124.

-- number of chromosomes in artificial parthenogenesis and in merogony, 125. De Vries : importance of potassium for turgor of plant-cells, 146.

Doncaster: hybrid Echinoid larvae, 26].

Driesch: effect of light in development, 94.

— abnormal segmentation in Erhinus produced by heat, 105.

— Anenteria, produced by heat, 106.

—- segmentation made irregular by dilution of sea-water, 118.

—— pressure experiments on Echinoid eggs, 37, 38, 185, 240.

—- cell-division suppressed by pressure and dilute sea-water, 55; and by heat, 105.

—nuclear division not qualitative, 186.

— blastomeres disarranged, 187, 188.

— isolated blastomeres of Echinoids, 190, 191, 193, 194.

— potentialities of animal and vegetative cells, 193, 194, 201, 242, 243.

— fragments of blastulae and gastrulae in Echinoderms, 194.

— potentialities of ectoderm and agghenteron, and their limitations, 1 .

— development of egg fragments of Echinoids, 195, 196.

— germinal value, surface-area of larvae, and number of cells, 197199, 269.

— one larva from two blastulae, 202.

— and Morgan : isolated blastomeres of Ctenophora, 210, 211.

—2e1gg-fragments of Ctenophora, 30,



Drgggchz development of Myzostoma,

— isolated blastomeres and parts of larvae in Phallusia, 288, 289.

— first furrow and sagittal plane in Echinoids, 250.

— characters which depend on cytoplasm in Echinoid larvae, 261, 262.

— number of organ-forming substances in cytoplasm, 246, 284, 286.

—— theory of egg-structure, 281, 286, 292.

— reason for limitation of potentialities, 192-194, 201, 212, 242, 243, 281, 282, 284, 291.

--fate a function of position, 188, 282.

—- return of displaced mesenchyme cells in Echinus, 274.

- stimuli in ontogeny, 20, 277, 28"284.

— part played by nucleus in differentiation, 266, 284, 285.

—— equipotential and inequipotentiul systems, 176, 277, 285.

— rhythm of development, 3.

—- harmony of development, 284.

—- composition in development, 3, 285.

— self-difierentiation, 284.

—- teleology, static, 286, 291, 292, 297.

— —- dynamic, 291, 292, 297.

— vitalism, 20, 289 sqq.

Edwards : physiological zero for Home egg, 102.

-- growth without differentiation, 104.

Endres and Walter : post-generation of missing half-embryo, 171.

Eycleshymer: first furrow sagittal plane in Necturus, 168.


Fabricius : views on development, 13.

Fasola : electric currents, 91.

Fehling : growth of the human embryo, 59, 60, 63.

Feré : effect of sound-vibrations upon the Chick, 90.

_ ._ of light, 96.

— malformations due to high temperatures, 105. .

—- need of oxygen for the Chick, 109.

—— monstrosities produced by various chemical reagents, 18,2. INDEX OF AUTHORS

Fischel, A. : hybrid Echinoid larvae, 261.

— variability of Duck embryos, 71.

Fischel, H. : isolated blastomeres of Ctenophora, 210, 211.

-— derangement of blastomeres in Ctenophora, 211.

Fischer: artificial parthenogenesis, 124. ’ Foot : polar rings in Allolobophom,


Garbowski : function of pigment ring in Strongylocentrotus egg, 192. — first furrow and sagittal plane in

Echinoids, 260.

— grafting of blastulae fragments of Echinus, 202.

Gerassimow: size of nucleus and cells in Spirogyra, 269.

Giacomini: need of oxygen for the Chick, efiect of low atmospheric pressure, 109, 110.

Giardina : difierentiation of chromatin in female cells of Dytiscus.

Godlewski : the respiration of the Frog’s eg, 110, 112, 113.

-— heterogeneous cross-fertilization, 262.

Graf : fusion of blastomeres, 56.

Greeley: artificial parthenogenesis produced by cold, 108.

— low temperatures and absorption of water, 108.

Grobben : Cetochilus, 22.

Groom : effect of fertilization in Cirripedes, 250.

Gigiber: regeneration in Protozoa,


Gurwitsch : monstrosities produced in Amphibian embryos by chemical reagents, 120, 123.

Hacker : Cyclops, 22.

Haeckel: recapitulation, 16.

— development of fragments of blastulao of Crystallodes, 181, note. Hr;ller : preformation and epigenesis,


Harvey: epigenesis, 13.

— metamorphosis, 14.

Hecker: growth of the human embryo, 62, 63.

Hansen: growth of guinea-pig embryos, 62.

Herbst : potassium, sodium, and lithium larvae of Echinoderms, 136-140.

—- significance of monsters for origin of variatiops, 141.


Herbst : necessity of elements present in sea-water for normal development of Echinoid larvae, 141 sqq.

—— separation of blastomeres of Seaurchins in calcium-free sea-water,


— stimuli in ontogeny, 20, 272, 273, 285.

— formation of Arthropod blastederm oxygenotactic, 114.

—— arms of Plutous due to presence of skeleton, 187, 138, 144, 149, 274, 275.

I-Ierl itzka, development of half-blastomeres of Newt, 173.

Hertwig, 0. : centrifugalized Frog’s egg, 29, 87.

—- rules for nuclear and cell division, 31, 32, 85.

— — confirmed by pressure experiments, 34-36.

— gravity and Echinoderm eggs, 78.

—— insemination of Frog's egg, 79.

— cardinal temperatures for Rana

fusca. and csculenta, 97.

— monstrosities produced by high and by low temperatures, 99.

— temperature and rate of development, 100.

—— monstrosities produced in Amphibian embryos by sodium chloride, 119, 135.

— first furrow and sagittal plane in Frog's egg, 165.

— compressedeggs: disproof of qualitative nuclear division, 34—86, 168, 169, 240.

— development of half-blastomere of Frog’s egg, 169.

— mutual interactions of developing parts, 271, 285.

Hertwig, 0. and R. : fertilization processes altered by heat and cold, 107.

— — by alkaloids, 126 sqq., 263.

His: mechanical explanation of development, 3.

—- germinal localization, 17, 158.

— the blastoderm oxygenoti-opic,114.

Hunter: artificial parthenogenesis by concentrated sea-water, 124.

Iijima: spiral asters in Nephelis egg, 40.

Jenkinson: pressure experiments on eggs of Antedon, 37, note.

— abnormalities of Frog embryos produced by various solutions not due to increased osmotic pressure, 120, 133-136. 318

Jenkinson: plane of symmetry, first furrow and sagittal plane in Frog's egg, 165-168.

Jennings: fertilization spindle in Asplanclma, 34.

Kaestner: cardinal temperature points for the Hen‘s egg, 102.

— malformations due to low tem~ peratures, 104. '

Kant : teleology, 286-289, 292, 297.

Kastschenko: injuries to blastoporic lip in Elasmobranchs, 178.

Kathariner: gravity and the gray crescent of the Frog's egg, 86.

King : cause of differentiation of lens, 276, 276.

Knowlton : sec Lillie and Knowlton.

Kolliker: 16.

Kopsch : first furrow and sagittal plane in Frog's egg, 165, 168.

—— efl'ect of injuries to blastoporic lip, 178.

Korschelt: fusion of ova in Ophryotmcha, 202.

— nucleus of egg-cell in Dyfiscus, 252. .

Kostanecki and Wierzejski: efi'ect of fertilization in Physa, 250.

Kowalewsky: 16.

Kraus : the role of water growth of plants, 58.

Lang : effect of fertilization in Polyclads, 250.

Leibnitz : preformation, 15.

Lewis: causes of formation of lens and cornea, 275, 276. Lillie and Knowlton: eflect of low temperatures in Amphibia, 100. — temperature and rate of development, 101.

Lillie: effects of salts on ciliary movement, 135.

— ghysiologically balanced solutions, 1 6.

in the

— toxicity and valency, 136.

Loeb : suppression of cell-division in Echinoids and Fishes, 56, 117. -— eflect of light in development, 94. —the respiration of Otmolabrua and

Fundulua eggs, 111.

—— the respiration of the ova of Echinoids, 112.

— function of oxygen in regeneration of Tubular-ia head and other processes, 114, 278, 274.

-— efi'ect of hypertonic solutions on Fundulus and Arbacia eggs, 117.

--exovates produced by dilute seawater, 118, 190, 194, 195.


Loeb: artificial parthenogenesis, 121, 124.

—- etfect of potassium cyanide in prolonging life of ova, 131, 132.

— eflect of certain salts on Fundulus embryos and on Plutei, 135.

— toxicity and antitoxicity functions of valency, 186.

-— effect of alkalies, 151.

— effect of gravity on Anmmularia, 272, 273.

-gégterogeneous cross-fertilization,

Lombardini : electric currents, 91.

Lyon : need of oxygen for the eggs of Arbacia, 112.

— action of potassium cyanide, 132.

Malebranche : preformation, 15.

Malpighi: preformation, 14, 15.

Marcacci : mechanical agitation of Hen's eggs, 90.

Mark: spiral asters in eggof Lz‘maac,40.

Mathews: artificial parthenogenesis by mechanical agitation, 90.

—— effects of atropine and pilocarpine on Echinoderm eggs, 131.

—toxicity and decomposition tension, 136.

— see also Wilson (E.B.)and Mathews.

Mencl : formation of lensin SaImo,276.

Metsclinikoif : separation of blastemeres of Oceania, 181.

-—fusion of blastulae in Mitrocoma, 202.

Minot : rate of growth defined, 60.

—— change of rate of growth of guineapigs, 61.

— - of rabbits, 62, 68.

— — ofchickens, 67.

— coeflicients of growth, 65.

— senescence, 65.

-- increase of cytoplasm, decrease of mitotic index, 65.

— change of variability in guineapigs, 71. _ — genetic restriction, 246, 277. Mitrophanow: malformations due to low and high temperatures, 104. — necessity of oxygen for the Chick, 109.

Moore : sodium sulphate an antidote to sodium chloride, 135, 186.

Morgan : suppression of cell-division in Arbacia, 56, 118.

- gravity and the gray crescent of the Frog's egg, 86.

-— monstrosities produced by low temperatures in Ranapaluslris, 100.

— need of oxygen for the Frog's egg, 110. INDEX OF AUTHORS

Morgan :lithium salts used to produce alzlgéiormalities in Frog's eggs, 120,

— attempts to induce parthenogenesis, 124.

— number of chromosomes in artificial parthenogenesis, 125.

— artificial parthenogenesis produced by cold, 108. — first furrow, plane of symmetry, and sagittal plane in Frog's egg, 165,168.

— development of half-blastomere of

Frpg's egg ; post-generation, 170,

17 .

— development of vegetative cells of Frog’s egg, 173.

— potentialities of half-blastomeres in Teleostei, relation of flrstfurrow tn sagittal plane, effect of removal of yolk, 178.

— effect of injuries to blastoporic lip, 179.

— number of cells in partial larvae of Amphioxus, 181.

— potentialities of ectoderm in Echinoids, 195.

— development of egg-fragments of Echinoids, 197.

— number of cells in partial larvae of Echinoids, 198.

— fusion of blastulae of Sphaerechinua, 201.

— and Driesch: isolated blastomeres and egg-fragments of Ctenophora, 210-212.

— micromercs of Ctenophore egg, 30.

—- characters of hybrid Echinoid larvae, 260.

Moscowski : gravity and the gray crescent of the Frog's egg, 86.

Miihlmann : prenatal growth-rate in man, 64.


Nfigeli : permutations of original elements in development, 286.

Pander: 16.

Pearson : variability in man, 73.

Pfliiger: isotropy of the cytoplasm, 18, 158.

—--influence oi’ gravity on development, 18, 78, 81-83, 168.

-- rule for direction of nuclear division, 32, 85.

Plateau : principle of least surfaces, 41, 43.

Platnerz 280.

Pott : growth of the Chick, 59, 60, 67.


Pott and Preyer: respiration of the Chick, 112. — loss of weight of Hen’s egg due to evaporation from albumen, 115. Preyer : rate of growth, 60.

Quetelet: change of rate of in man (weight), 68.

— — (stature), 69.

— — (other dimensions), 90.


Rauber : efiect of reduced atmospheric pressure on the Frog’s egg, 110.

— elfect of pure oxygen on the eggs and tadpoles of the Frog, 118, 114.

Reichert: 16.

Remak : 16.

Robert : mechanics of spiral segmentation, 45-47.

— rate of growth in man, 68.

—-— change of variability, 73.

Rossi : efi‘ect of electricity on Amphibian eggs, 91.

Roux : aims of experimental embryology, 13.

— ‘Mosaik-Theorie ’ of self-differentiation, 17, 158, 279, 286, 297.

— qualitative nuclear division abandoned, 19, 159, 240.

— idioplasm and reserve-idioplasm, 159, 266.

— a half-embryo from one of first two blastomeres and post-generation of missing half, 159, 162.

— coincidence of first furrow and sagittal plane in Frog's egg, 17, 159, 165. '

— the spermatozoon and symmetry of the Frog's egg and embryo, 80, 165, 247, 248.

— meaning of karyokinesis, 252.

— dependent diflerentiation, 17, 158, 277, 286.

— functional adaptation, 290.

-— specific gravity of contents of Frog’s eg, 79.

—- gray crescent of Frog's egg, 80, 165.

— influence of gravity on the Frog's egg, 85-87.

— effect of electricity upon the Frog’s egg, &c., 92.

— light and development, 93.

— segmentation of Rana esculenta, 26.

—- Frog's eggs compressed in small tubes, 39, 40.

— comparison of systems of oil drops and segmenting ova, 49-58.

— cytotropism, 55, 278. 320

Roux: cytotaxis, 55.

— cytochorismus, 45.

-— cytarme, 45, 53.

— cytolisthesis, 58.

— ‘ Framboisia’, 135.

Ruseoni : electric currents, 91.

Sachs : law of direction of cell division, 28.

Sala: fertilization processes altered by cold, 108.

- fusion of the eggs of Ascaris, 202.

Samassa: effect of pure oxygen at

pressures on the Frog's egg,

— effect of lack of oxygen on the Frog's egg, 119.

— effect of various gases on the eggs of Ascaris, 112.

—development of animal cells of Frog's egg, 173.

— Schaper: development of tadpoles after removal of brain and eyes, 175.

—- cause of differentiation of lens, 275.

Schulze, F. E. : Sponges, 22. Schulze, 0.: gray crescent of Frog’s

eg, 80, 247.

—— gravity and the Frog’s egg, 86.

—- effect of low temperatures on the Frog's egg, 100.

—— first furrow and sagittal plane in Frog's egg, 165.

— double monsters from Frog’s egg, 171.

Seeliger : hybrid Echinoderm larvae, 260, 269.

Selenka: first furrow and sagittal plane in Echinoids, 250.

Semper: rate of growth in Limnaea, 67.

Smith: Peltogaster, 24.

Sollmann : after effects of hypertonic solutions, 124.

Spemann : development ofconstricted Newt's eggs, and embryos, 174, 175.

— causes of formation of lens and cornea, 275, 276.

Sumner: injuries to blastoporic lip of Teleostei, 178, 246.

Sutton {individuality of chromosomes in Brachyslola, 256.

Swammerdam : preformation, 14, 15.

segmentation of

Vejdovsky : unequal centrosomes in dividing pole-cells, 31.

— polar rings in Rhym.-hclmis, 251.

Vernon: rate of growth in Strongmlocmtrotus, 67, 70.


Vernon : alteration of variability in Echinoid larvae, 71, 74.

-— effect of light on Echinoid larvae, 95, 96. '

— effects of change of temperature on Echinoid larvae, 106, 107.

-— change of variability produced by heat, 107.

— and by chemical agency, 141, 156.

—poisonousness of carbon dioxide to Sea-urchin eggs, 112.

— characters of hybrid Echinoid larvae, 261.

Verworn : behaviour of Protozoa in an electric current, 93.

— regeneration in Protozoa, 254, note.

Walter, sec Endres and Walter.

Weber : law of stimuli, 272.

Weismann: qualitative division, 19, 297.

— idioplasm, and reserve—idioplasm, 159.

Weldon : growth-rate in Carcinus, 71.

— change of variability in Carcinus, 72.

— — in Clausilia, 73.

Wetzel : double monsters Frog’s egg, 172, 245.

Whitman : polar rings in Clepsine, 251.

Wierzejski, see Wierzejski, 250.

Wilson, 0. B. : malformations of Amphibian embryos, 120.

— acclimatizution to salt-solution, 136.

Wilson, E. B. : phioxus, 26.

—— segmentation of Renilla, 55, note.

— unequal centrosomes in dividing pole-cells, 31.

—pressure experiments on eggs of Nareis, 39, 213, 240.

- cytology of artificial parthenogenesis, 124.

— development of isolated blastemeres in Amphioxus, 179, 180.

—— isolated blastomeres of Oerebratulus, and fragments of blastulae, 205, 206.

— isolated blastomeres of Patella, 218-222.

—- of Dentalium, 225, 226.

—— removal of polar lobe, 224.

— effect of fertilization, 222, 223.

— development of egg-fragments, 226, 227.


from Kostanecki and segmentation of Am

Wilson (E. B.) and Mathews : spermpath, egg axis, fix-st furrow, and embryonic axes of Toacopneustes, 185, 249, 250. ‘

Windle: effect of magnetism and electricity on development, 91.

Wolff : epigenesis, 16.

Yatgu: egg-fragments of Cerebratulus, 27.

Yung: effect of light on tadpoles, etc., 94.

Zeleny : egg-fragments of Cerebratulus, 206, 207.

Zelinka : fertilization Callidma, 34.

spindle in

Jnxntsonr’ Y

Ziegler : heterodynamic centrosomes, 80.

.— formation of micromeres in Cteno phora, 209, note.

-— pressure experiments on egg gaéiinoids and Ctenophora,

— fertilization of Diplogaster, 84.

— egg and embryonic axes, 250.

Zoja : isolated blastomeres of Hydromedusae, 181, 182.

—— animal and vegetative cells of Strongylocentrotus, 198.

Zur Strassen : segmentation of Asoaiis, 81.

— fusion of the eggs of Ascaris.

Jenkinson (1909): 1 Introductory | 2 Cell-Division and Growth | 3 External Factors | 4 Internal Factors | 5 Driesch’s Theories - General Conclusions | 6 Appendices

Cite this page: Hill, M.A. (2024, April 17) Embryology Book - Experimental Embryology (1909) 6. Retrieved from

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