No. 2.] COMPARATIVE CYTOLOGICAL STUDIES. 269 



leicht bildet das Material des Keimblaschens und der Keim- 

 flecke die Grundlage zum serosen Blatt und zum Fruchthof 

 der Keimhaut." (Jones, '35, '37, does not mention the nucle- 

 olus; accordingly, he is not the discoverer, as is claimed by 

 Bischoff.) 



Valentin ('36, cited by Carnoy, '84) describes the nucleolus 

 as a " rundes Korperchen, welches eine Art von zweitem Nucleus 

 bildet." (On this historical ground Carnoy considers the term 

 "nucleolus" should be limited to his " nucMole-noyau.") 



Valentin ('39, mentioned by Carnoy, '84) introduces the 

 terms "nucleolus" and " Kernkorperchen " ; the latter term 

 was proposed also by Schwann ('39) in the same year. 



Bischoff ('42) found in the egg of the rabbit one nucleolus, 

 "ein schwach granulirtes Kornchen," which he considers to be 

 a " Zellenkern." 



Vogt ('42) found several nucleoli (six to twelve) in the ova of 

 Coregonus ; these subsequently migrate into the yolk to form 

 the first cells of the blastoderm. 



Leydig ('49) describes in the germinal vesicle of Nephelis 

 one nucleolus, in Clepsine one or numerous ones, in Piscicola 

 two to four, while in Hae^nopis " der Keimfleck war einfach, 

 8-formig oder doppelt." 



Kolliker ('49) studied numerous Gregarines, and concludes 

 that the nucleoli ("Kornchen") "bei manchen Gregarinen 

 gewisse bestimmte Entwickelungen durchlaufen, namlich bei 

 jungen Individuen einfach vorhanden sind, bei alteren allmalig 

 in zwei, drei oder mehr Korner zerfallen." In G. terebellae, 

 clavata, saenuridis, and etichytraei there is a single nucleolus ; 

 G. sipwicidi has from one to six ; G. heeri, six to eighteen ; 

 G. sieboldii, one to seven, which are either homogeneous or 

 vacuolar, or else only one or two are present, and each of these 

 is composed of a mass of smaller ones ; G. brevirostra has from 

 six to nine nucleoli. 



Lov^n ('49) studied the eggs of Modiolaria, Cardium, 

 Patella, and Soleti, and found that during the process of 

 fecundation the nuclear membrane ruptures, and the nucleolus 

 passes out through the vitelline membrane. (It is very prob- 

 able that he confused the nucleolus with a pole body.) 



