424 BULLETIN OF THE 



considered as the equivalent of the canal cell of conifers. The so-called 

 " Fadenapparat " of the egg of angiosperms has also rightly been held 

 in Strasburger's opinion to be homologous with the canal cells. 



Strasburger concludes (pp. 304, 305) that a part of the germinative 

 vesicle in the animal egg always remains behind, but that this relic does 

 not correspond to the germinative dot. Thus it is more than probable 

 that there is an agreement with corresponding processes in plants, 

 where one half of the divided egg nucleus is eliminated, and the other 

 half is modified in one way or another, and may even become indistin- 

 guishable. 



Priestley ('76) gives a purely objective resume of the papers of Auer- 

 bach (74), Strasburger (75), 0. Hertwig (75), and Van Beneden (75). 



Greeff (76", pp. 85-87) takes a position intermediate between Van 

 Beneden and 0. Hertwig. He in the main corroborates for Asteracan- 

 thion Van Beneden's observations, by saying, that the germinative dot 

 first suffers a conversion into granules, that the vesicle then begins to 

 diminish in size and distinctness, and that finally both appear to 

 vanish ; and then he concludes by saying, " One cannot positively deny 

 that the germinative spot persists, and, in migrating through the yolk, 

 amoeba-like, becomes so indistinct as to be no longer distinguishable." 

 He also reports that eggs of A. rubens carefully guarded from fecunda- 

 tion develop in the normal manner, but considerably slower than fecun- 

 dated eggs (pp. 83-85). 



Selenka (76", p. 167) writes of the freshly deposited eggs of Cucuma- 

 ria, that they no longer possess a nucleus, but exhibit at times "a little 

 drop of protoplasm under the egg capsule, — perhaps the excrement of 

 the egg.^' This is probably to be considered the polar globule. "In 

 the course of one or a few hours a clear nuclear area (Kernhof) becomes 

 visible in the interior, in the middle of which arise new nuclei, composed 

 of eight to twenty small bodies (Kernkeime, Goette) united in the form 

 of a mulberry." Up to a stage consisting of thirty-two segmentation 

 spheres the same peculiar groups of Kernkeime are met with. After- 

 wards the nuclei take the form of smooth balls, destitute of enveloping 

 clear areas. 



Salensky (76, p. 185, Taf XIV. Fig. 5) figures an egg of Salpa 

 in which two nuclei [the pronuclei] occupy the opposite poles. I 

 believe Salensky is wrong in holding the presence of these nuclei to be 

 evidence of approaching segmentation. 



Zeller (76, pp. 255 - 260, Taf XVIII. Figs. 21-31) gives an interest- 

 ing account of the processes accompanying cell division, and also some 



