1884.] 53 [Hyatt. 



shaped striated bodies which act more or less in concert with the 

 products of the division of the nuclei or secondary nuclei, remind 

 us forcibly of the different spindles which appear during the 

 development and segmentation of the egg. But this has not 

 been fully traced out, and we do not know what the morphol- 

 igical resemblance signifies, farther than that it indicates identity 

 between the products of the primitive sexual segmentation of 

 nuclei in Protozoa and the agamic segmentation of the same part 

 in Metazoa. 



Engelmann (Morph. Jahrb. 1, 1876, p. 628) unites with Biitschli 

 in the opinion that the nucleus and nucleolus are products 

 of one and the same body, the primitive nucleus, that they 

 have different sexual functions in the Protozoa, and in their 

 united form are strictly homologous, functionally and structurally, 

 with the nucleus of the ovum. This author, however, considers 

 the nucleolus as being probably devoted to the purely male func- 

 tion of being interchanged during copulation. This seems prob- 

 able, since in many forms after conjugation the nucleolus disap- 

 pears, apparently becoming united with the nucleus, and only 

 reappears again just before the breeding period, apparently aris- 

 ing from division of the homogeneous nucleus. 



Biitschli, in one of his last articles, contends that there is no 

 elimination of male or female elements during conjugation in the 

 nucleus of the Protozoa, and that the bisexual character of the 

 nucleus cannot be assumed on this ground. He also thinks that 

 the assumption of bisexuality for the ovum is not accordant with 

 the phenomena of parthenogenesis among plants and possibly 

 among animals. 



Dr. Whitman gives a resume of Biitschli's, Engelmann's and 

 Hertwig's views on the bisexuality of the nucleus, and evidently 

 does not regard Biitschli's objections as very strong. In fact it 

 is very difficult to account for the differentiation of the nucleus 

 and spindle bodies (nucleoli) in Protozoa and the difference 

 of structure admitted by Btitschli, by any other supposition, than 

 that they are the first sign of sexual distinction arising by 

 differentiation from the sexless, homogeneous nucleus. 



Hertwig appears to have been the first to show that the fecun- 

 dation of the egg was accomplished by the union of the male pro- 

 nucleus formed from the spermatozoon after its passage into the 



