DEVELOPMENT OF ELASMOBRANCH FISHES. 23 



in the later stage, was the commencement of this new 

 nucleus. Gotte^ has figured structures somewhat similar to 

 these bodies, but I hardly understand either his figure or his 

 account sufficiently clearly to be able to pronounce upon the 

 identity of the two. In case they are identical, Gotte gives a 

 very different explanation of them from my own^ 



A second of my results, which points to a series of inter- 

 mediate steps between division and solution of the nucleus, is 

 the distribution in time of the peculiar cone-like bodies. These 

 are present in fair abundance at an early period of segmen- 

 tation, when there are but few nuclei either in the blastoderm 

 or the yolk. But at later periods, when there are both more 

 nuclei, especially in the yolk, and they are also increasing in 

 numbers more rapidly than before, no bodies of this kind are 

 to be seen. This fact becomes the more striking from the 

 lobate appearance of the later nuclei of the yolk, an appearance 

 which exactly suits the hypothesis of the rapid budding off of 

 fresh nuclei. 



The observations of R. Hertwig' on the gemmation of Podo- 

 phrya Gemmipara, support my interpretation of the knobbed 

 condition of the nuclei. Hertwig finds (p. 47) that 



The horse-shoe shaped nucleus grows out into numerous 

 anastomosing projections. Over the free ends of the projections little 

 knobs appear on the surface of the body, into which the lengthening 

 ends of the processes of the nucleus grow up. Here they bend 

 themselves into a horse-shoe form. The newly-formed nucleus then 

 separates from the original nucleus, and afterwards the bud contain- 

 ing it from the body. 



From the peculiar arrangement of the net-work of lines of 

 the yolk around these knobbed nuclei, it is reasonable to con- 

 clude that interchange of material between the protoplasm of 

 the yolk and the nuclei is still taking place, even during the 

 later periods. 



These facts about the distribution in time of the cone-like 



1 Enticickhingsgeschichte der Llike, PI. i. fig, 18. 



2 As I before mentioned, Strasburger (ZellUldang u. Z elWheilung) hag repre- 

 sented bodies precisely similar to those I have described, which api^ear during 

 the segmentation in the egg of Phallusia MammiUata as well as similar figures 

 observed by Butschli in eggs of Cucullanus elegans and Blatta Gcrmanica. The 

 figures in this monograph are the only ones I have seen, which are identical 

 with my own. 



' Morphologisches Jahrbuch, Bd, i, pp. 46, 47. 



