No. 2.] COMPARATIVE CYTOLOGICAL STUDIES. 451 



formation and fuse with the former. Were these secondary 

 nucleolar globules in Lineus as large as the first-formed 

 nucleolus, and were they all to remain separate from one 

 another, the nucleolar metamorphosis in this genus would 

 correspond to that of the metanemerteans ; accordingly, the 

 difference in the nucleolar production is not very important. 

 (For the nucleolar relations in the other nemerteans, cf. my 

 reviews of the papers of v. Kennel, Hubrecht, Coe and Biirger.') 



9. Siphonophore {Rodalia ?). 



(Plate 26, Figs. 204-212.) 



(Dr. Conklin kindly loaned me the preparations on which his 

 earlier studies were based ('91) ; these were preserved in alcohol 

 and stained with haematoxylin.) 



There were no very young stages of the ovogenesis in this 

 specimen ; I have studied the ova in the egg pouches and in 

 the gonophores, each gonophore containing a single large ovum 

 (as shown by Conklin and Brooks), while in the egg pouches a 

 number of smaller ova may be present. 



A single large nucleolus is contained in each germinal 

 vesicle. This is not only large in relation to the size of the 

 nucleus, but is also absolutely probably one of the largest 

 nucleoli ever described in animal cells (Fig. 212). It is always 

 excentric in position, though seldom close to the nuclear mem- 

 brane. In those younger stages where the nucleus is still near 

 the center of the egg (Fig. 205, and the dorsal cell of Fig. 211) 



^ The only other observations of the yolk development in the nemerteans are 

 those of Burger ('90) on Drepatiophorus. Near the young germinal vesicle lies in 

 the cytoplasm a homogeneous, deeply staining body, of smaller size than the 

 nucleus, which Biirger assumes may correspond to a yolk nucleus. This body 

 disappears, " und e? sammeln sich namlich, dem Keimblaschen anliegend, in jenem 

 [Plasmahiigel] kuglige oder langliche, tropfchenahnhche Gebilde an, erst sparlich 

 ein einziges, zwei und mehrere, spater aber mit dem immer noch fortschreitenden 

 Wachstum des Keimblaschens sich zahlreich vermehrend in grbsster Menge. .Sie 

 sind durchaus homogen, von mattem Glanze und ausserst tinktionsfahig. . . . 

 Erst nach der Entwicklung des Keimblaschens geht die des Deutoplasmas vor 

 sich und zvvar nun auf Kosten der glanzenden Dotterballen, welche aufgebraucht 

 werden und so im reifen Ei verschwinden." In the ripe egg the cytoplasm is 

 granular and stains lightly. 



