No. 2.] COMPARATIVE CYTOLOGICAL STUDIES. 275 



pearance in ripe ova." A 1.5/fc solution of NaCl gives rise to 

 vacuoles in the nucleoli (this antedates the observation of 

 Morgan, '96). 



Van Beneden ('69) studied Gregarina gigantca: " Le nombre 

 de nucleoles varie a chaque instant ; quelques-uns disparais- 

 sent, tandis que d'autres se forment ; ils apparaissent sous 

 forme d'un petit point presque imperceptible ; ce point grandit 

 jusqu'a certaines limites ; il devient un veritable corpuscule 

 forme d'une substance homog^ne tr^s-refringente, puis le 

 corpuscule diminue de volume ; il r^fracte de moins en moins 

 la lumiere, enfin il disparait." 



Clapar^de ('69) found in the egg of Lumbriciis tcrrestris 

 that the nucleolus " ist doppelt, indem er aus zwei einander 

 beriihrenden ungleich grossen Kiigelchen besteht." 



iB-o-jg. 



Eimer ('71), epithelial cells of the snout of Talpa : each 

 nucleolus is surrounded by a clear space ("Hof"), and the 

 outer boundary of this space " war bezeichnet durch zahl- 

 reiche kleine Punktchen. ... Im optischen Querschnitt 

 stellten diese Kornchen einen Kreis um den hellen Hof des 

 Kernes dar." 



Eimer ('72) finds in the earlier stages of the egg of Lacerta 

 that all the nucleoli are grouped near the center of the 

 nucleus, while in more advanced ova there are numerous larger 

 peripheral nucleoli, and smaller ones in the other portions of 

 the nucleus ; around each of the large peripheral nucleoli are 

 situated concentric rows of smaller ones. Here, as well as in 

 Cistudo, Testudo, and Tropidonotus, the smallest nucleoli are 

 homogeneous, while the larger contain vacuoles. He con- 

 cludes that " die complicirt gebauten Keimflecke aus einfachen 

 Kornchen" are built up. 



Kleinenberg ('72) : in the egg of Hydra the single spheri- 

 cal nucleolus contains " ein auffallend stark lichtbrechendes 

 Korperchen. . . . Nach kurzer Zeit schwindet es wieder." 

 The nucleolus then becomes irregular in form, breaks into 

 small granules, and he supposes that these latter become 

 dissolved. 



