No. 2.] COMPARATIVE CYTOLOGICAL STUDIES. 291 
egg nucleus : “ Ce nucleole a une tendance bien evidente a se 
placer dans le voisinage immediat des noyaux folliculaires en 
voie de formation. Le fait n’est pas constant, mais il est trop 
frequent”; he did not actually observe that the nucleolus gives 
off a part of its substance to the follicle cell, but supposes this 
to be the case. 
Fol, in a second paper (’ 83 b) of the same year, finds that in 
Ciona during the “production endogene” of the follicular cells 
a segment (diverticulum) of the egg nucleus breaks off, while 
the (then peripherally situated) nucleolus gives a part of its 
substance into this diverticulum, and the nucleolus then wanders 
back to another portion of the nucleus. “Chez Ascidia mam - 
viillata , le bourgeonnement de l’enveloppe a lieu simultanement 
en une foule de points, et il est tout ou moins admissible que la 
substance de la tache germinative dispersee a la formation de 
ces bourgeons.” 
Gruber (’ 83 ) describes in Actinosphaerium the growth of a 
supposed nucleolus and its division during mitosis into two 
equatorial plates; though his figures would show that he 
mistook true chromatin masses for a nucleolus. 
Jensen (’ 83 ) studied the ovum of Cucumaria; there are from 
fifteen to thirty nucleoli flattened against the nuclear membrane, 
and containing vacuoles. As shown by treatment with acetic 
or picrosulphuric acid, the outer layer of the nucleolus seems to 
be a continuation of the nuclear membrane, so that the inner, 
less refractive portion of the nucleolus appears to be situated in 
a depression of the outer surface of the nuclear membrane. 
La Valette St. George (’ 83 , quoted after Platner, ’86) found in 
the egg of an Isopod one nucleolus which is at first homogene¬ 
ous, later granular, and which may enclose a vacuole and show 
amoeboid movements. In other cases there are either several 
smaller vacuoles or one or two larger ones. 
Leydig (’ 83 ), from comparative studies, concludes that the 
nucleoli “sind Theile des Kernnetzes,” and that each of them 
is enclosed in a small, clear cavity of the nucleus. “ Die Nucle¬ 
oli konnen als eine Vielzahl von Kornchen erscheinen, die 
unter sich gleichwerthig sind. . . . Nicht selten lasst sich bei 
genauem Zusehen in der Menge kleiner und unter sich gleicher 
