No. 2.] COMPARATIVE CYTOLOGICAL STUDIES. 
2 75 
pearance in ripe ova.” A 1 . 5 ^ solution of NaCl gives rise to 
vacuoles in the nucleoli (this antedates the observation of 
Morgan, ’96). 
Van Beneden (’69) studied Greganna gigantea: “ Le nombre 
de nucldoles varie 4 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-rdfringente, puis le 
corpuscule diminue de volume ; il refracte de moins en moins 
la lumiere, enfin il disparait.” 
Clapar&de (’69) found in the egg of Lumbricns terrestris 
that the nucleolus “ ist doppelt, indem er aus zwei einander 
beriihrenden ungleich grossen Kiigelchen besteht.” 
1870-yg. 
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 Piinktchen. . . . 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. 
