Hyatt.] 52 [March 5, 



nucleus is formed, remaining in the individual after the resorp- 

 tion or exclusion of the unnecessary part of the nucleus, and 

 finally, that the striated spindle-shaped bodies of the nucleolus 

 become united with the female pronucleus forming a new 

 nucleus. " There is, therefore," according to this author, " no diffi- 

 culty in comparing the conjugation of Infusoria with the fecun- 

 dation of the egg.^ 



This author originated the opinion, that as in the egg among 

 Metazoa, the effect of conjugation among the Protozoa is the 

 inauguration of a period of intensified reproduction by self-divis- 

 ion. He thus made another comparison between the effects of 

 fecundation in the egg, and those of conjugation in unicellular 

 animals. He here abandons the opinion formerly held that the 

 nucleolus is a sperm-producing, and the nucleus an egg-produc- 

 ing, organ among Protozoa, and takes up the same view, so far 

 as the bisexual nature of the nucleus is concerned, as has been 

 taken by Hertwig, and Engelmann. 



Butschli has really done more than any other author in his 

 extended comparisons of the phenomena attending fecundation 

 in the eggs of Metazoa, and conjugation in the bodies of Proto- 

 zoa Ciliata. In Abh. Senck. nat. Geselsch. vol. x, 1876, he shows 

 the essential morphological similarity of these processes, and also 

 extends the comparison to the division of cells in the Metazoa, 

 showing that as in the Infusoria the division of the nuclei which 

 precedes segmentation of the cell is accompanied by the forma- 

 tion of a connective or direction spindle, and that the plane of 

 division passes through the transverse differentiated zone of the 

 direction spindle in all cases whether in eggs, blood corjmseles, 

 spermatocysts or bodies of the Infusoria. 



This author regards the so-called nucleolus of Protozoa as dif- 

 ferentiated from the nucleus and compares the disappearence of 

 parts of the old nucleus after conjugation with the ejection of the 

 polar vesicles from the egg. In his view the nucleolus is really 

 the active agent of fertilization in conjugation and the nucleus is 

 the passive p6rtion of which parts disappear during this process. 

 He, however, denies that the nucleolus alone is exchanged espec- 

 ially in the conjugation of Vorticella. 



The transformation of the neucleoli of Protozoa into spindle- 



