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 “ nucteole-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 Haemopis “ 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 zerfalien.” In G. terebellae , 
clavata , saenuridis> and enchytraei there is a single nucleolus ; 
G. sipunculi 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. 
Loven (’ 49 ) studied the eggs of Modiolaria , Cardmm , 
Patella , and Solen, 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.) 
