294 MONTGOMERY [Vol. XV. 



substance during the following mitosis ; wherefore he suggests 

 the term " Prochromatin " for nucleolar substance. In the pro- 

 phase of the mitosis only one nucleolus is present in the 

 nucleus, while in the " Riickkehr der Tochterkerne zum Ruhe- 

 stadium waren dagegen stets mehrere vorhanden. In einem 

 gewissen Stadium, wo die Nucleolenbildung beginnt, ist eine 

 ganze Anzahl vorhanden ; jemehr sich der Tochterkern dem 

 Ruhestadium nahert, desto mehr vermindert sich die Zahl 

 unter gleichzeitiger bedeutender Grossenzunahme der iibrigge- 

 bliebenen, bis fiir das ausgesprochenste Ruhestadium das Vor- 

 handensein eines einzigen grossen central gelegenen Nucleolus 

 geradezu typisch wird," and this he concludes to be a process 

 of fusion. The nucleolus plays only a passive role in mitosis, 

 " namlich die eines aufgespeicherten Nahrungsmaterials zur 

 Neubildung von Chromatin." 



Rein ('83) studied the eggs of Lep2is and Cavia. In each 

 there is one large nucleolus which disappears during matura- 

 tion and is succeeded by several smaller ones, which have the 

 same consistency as the first, and at the time of their first 

 appearance occupy a central position in the nucleus. " So weit 

 ich den Vorgang am Saugethiere verfolgen konnte, machte mir 

 derselbe eher den Eindruck eines successiven Zerfalles des 

 urspriinglichen Keimfiecks in immer kleinere Stiickchen, welche 

 schliesslich in der Substanz des Keimblaschens verschwinden." 



Roule's ('83) conclusions are, in the main, confirmatory of 

 Fol's ('83) observations in regard to endogenous cell formation. 

 In the Qg^ of Ciona there is one large and two or three smaller 

 nucleoli, the latter being " formes pendant revolution des 

 cellules endotheliales en cellules ovulaires." In eggs a little 

 larger these " nucleoles adventifs " become more numerous (five 

 to six), and certain of them show a limiting membrane. Later 

 still some of these adventive nucleoles are found in the yolk, 

 where each becomes surrounded by a clear zone ; these he con- 

 siders at this stage to be the nuclei of endogenetically formed 

 cells (follicular cells), the clear zone around each representing 

 its cytoplasm. 



Schauinsland ('83) noticed in the tg'g of Distomum a single 

 large nucleolus. 



