MUSEUM OF COMPARATIVE ZOOLOGY. 301 



There is one point in Goette's account which seems to me cor- 

 roborative of the views I hold about the nature of the asters. The 

 fine-granular area surrounding the nuclear germ elongates before the 

 latter undergoes any change of form. Whitman ('78") has observed a 

 similar instance in the case of Clepsine, but has interpreted the elon- 

 gating area as a nucleus, I believe that Goette's nuclear germ and 

 Whitman's nucleoli, bxq the same, and are really nuclei, and consequently 

 that the " granular area " of the one and the " nucleus " of the other 

 are both cell protoplasm, so that in these two cases the first optical evi- 

 dence of a coming division is manifested, not in the nucleus, but in the 

 protoplasm immediately surrounding it. 



Very little attention is bestowed by Kowalevsky ('75, pp. 609, 610) 

 on the changes in the nucleus and cell protoplasm during segmentation, 

 as observed in Pyrosoma. The first division of the formative yolk is 

 effected by a furrow, which, beginning on one side, sinks deeper and 

 deeper, and near which is observed in each segmentation ball a nucleus 

 of stellate form (Fig. 13). An examination of the figure is sufficient to 

 convince one that the author has overlooked the real nucleus, and has 

 taken therefor the stellate figures in the protoplasm of the cell. The 

 reader will recall the fact that Kowalevsky had previously ('71) main- 

 tained that the stellate structure was limited to the nucleus, and will not 

 be surprised to find that this opinion has caused him to portray these 

 figures with an abruptness of outline (Fig. 14) which is not often seen. 

 The rays in the figure alluded to are even made to terminate distally in 

 slight enlargements.* Nothing in the figure would indicate that this 

 observer saw anything of the spindle-shaped condition of the nucleus, or 

 of the nuclear plates, which is the more surprising, if staining was re- 

 sorted to for these earlier stages, as it certainly was for later ones.f 

 The author thinks it probable that a division of the nucleus precedes 

 that of the yolk, although he has not directly observed it. 



* Although Eimer ('77, Figs. 13, 18, etc.) has recently shown that similar nuclei 

 are found in tissue cells, and especially in Coelenterates, I am still inclined to think 

 that Kowalevsky's "nuclei" are stellar arrangements of the cell protoplasm, such 

 as exist in the case of many other animals. 



t If I am wrong in considering these radiate lines as belonging to the protoplasm 

 rather than to the nucleus, then they probably can only be considered as the spindle 

 fibres of a nuclear spindle seen endwise, much as depicted by Strasburger ('76, Taf. 

 VII. Fig. 18 a). There is, however, a serious objection to this explanation, for two of 

 the cells in Fig. 14 (Kowalevsky) are in an advanced stage of segmentation, and are 

 50 located, with respect to the observer, that the spindle could have been seen only 

 'Mface, — not end- wise ! 



