MUSEUM OF COMPARATIVE ZOOLOGY. 561 



phiaster arise in substantially the same manner, — a thing which no one will 

 be inclined to question, and which Perez has himself assumed (pp. 392, 393) to 

 be true, — then the observations on Limax have an important bearing on the 

 point in question. I have shown that the stars arise not only outside the nu- 

 cleoli, but even outside the nuclei, at a time when there is no evidence of an. 

 interruption in the continuity of the nuclear membrane. It is therefore impos- 

 sible to ascribe the stars to the attractive influence of any morphologically 

 distinguishable portion of nucleus or nucleolus. If any part of the substance 

 previously contained in the nucleus occupies the centre of the stars, it must 

 have suffered changes entirely incompatible with the retention of its morpho- 

 logical integrity. 



My confidence in the real equivalency of the astral phenomena throughout 

 the animal kingdom is too strong to allow the belief that the eggs of Helix 

 differ in such essential matters from those of Limax. I am therefore compelled 

 to seek an explanation of the author's observations which shall be less at vari- 

 ance with evidence drawn from the study of other animals. 



He says that there always exist at the centres of the radiations small nuclei, 

 the grown-up nucleoli of the germinative spot. His own observations and fig- 

 ures, however, do not warrant the assertion.* Of the three figures (Figs. 16, 17 

 22) which he gives of amphiasters only one shows any central corpuscle, and 

 only one of the asters of that amphiaster is thus furnished. Figs. 15 and 18, 

 in which such structures are shown, are capable of a very different interpre- 

 tation from that given by Perez. But that is of less importance than to know 

 whether these corpuscles are derived directly from the germinative spot. I 

 therefore give the substance of the author's more extended account of the meta- 

 morphosis. " La vesicule [tache ?] germinative, d'abord uniformement brillante 

 (Fig. 6), perd son homogeneite ; elle se trouble, sans pourtant cesser d'etre 

 claire, par la production de granulations pales et mal limitees (Fig. 7). Au 

 milieu de ces granulations, on distingue ordinairement assez bien deux petits 

 nucleoles, que les reactifs rendent plus evidents. Ce sont la les premiers 

 signes de desorganisation de la tache." (p. 364.) Subsequently, as though 

 undergoing dissolution, it becomes pale, and is recognized with difficulty. 

 Meanwhile the germinative vesicle loses its sharp contour, its membrane be- 

 comes folded, and an instant later has entirely disappeared. Then there remains 

 only the protoplasm which it contained and the remnants of the disintegrated 



* When he speaks (p. 395) as though it were a matter of surprise that these cor- 

 puscles had not been recognized as existing in all cases at the centres of the asters, 

 one is not quite certain what can be meant. They^ certainly have long since been 

 seen, and have been recognized as occupying the centres of the asters. To cite a 

 single case, Flemming ('75, pp. 120, 191, Taf. III. Fig. 2) has shown that they exist in 

 Anodonta, and has moreover called attention to their deportment under the influence 

 of reagents. He has also stated that they are not constantly present. So far as I 

 can judge, Perez has not always found them, and my own observations seem to cor- 

 roborate the fact of their inconstancy. He has seen these corpuscles in the egg be- 

 fore treatment with reagents. I have not been so successful. 



VOL. VI. —NO. 12. 36 



