A Comparative Study of the Structure and Origin of the Yolk Nucleus. 701 
by Munson (62) in the tortoise. Kohlbrugge (43) regards a similar body 
in the egg of Mabuia multifasei the analogue of the nucleus of P ander in 
birds. According to him it is deutoplasm derived frora the germinal vesicle. 
Scharff (80) seems to believe that the inner, graniüar zone is due 
to extruded nucleoli. According to him, pouches are formed all over the 
germinal vesicle like pseudopodia of amoeba, into which the nucleoli are 
drawn; and these pouches thus constricted off, present the appearance 
of minute vesicles or cells containing a nucleus. Osiannskov has mistaken 
them for real nuclei. Sometimes the vesicles thus formed do not contain 
any nucleolar matter and remain unaffected by stains. Like the others, 
they move towards but do not quite reach the surface, leaving a cortical 
layer of protoplasm which is the Rindenschicht of His. Scharff seems 
to believe these bodies are finally eonverted into yolk. 
Will (94) found dark bodies in the cytoplasm which cause the cyto- 
plasm to take chromatin stain. Thus a stainable ring is found around 
the germinal vesicle, which is finally almost devoid of chromatin. Later 
this extruded chromatin is eonverted into yolk bodies. 
Bambeke (7) figures flamelike stainable bodies or substances coming 
out from the germinal vesicle, staining like chromatin, and surrounding 
the germinal vesicle as a ring. Speaking of the boundarv of the zones 
he says: “R s’agit ici, non d’une couche limite separant deux parties 
Constituantes du corps protoplasmique cellulaire ou ovulaire, ni de rempli 
d’une membrane, mais d’une condensation sous forme de faisceau du 
reticulum cellulaire.” 
In his earüer publications Balbiani regarded the yolk nucleus as due 
to cells entering the egg, but later he maintained that it was due to ex- 
truded nuclear material. Finally (4) he came to the eonclusion that it 
is the centrosome and sphere. 
Says Hexxeguy (32): “Cet element provient donc, chez les Ver- 
tebres, de la vesicule germinative, comme M. Balbiani l’a c-onstate pour 
les Invertebres, chez les Geophiles. C’est tres probablement une partie 
de la tache germinative ou une tache germinative entiere qui sort de la 
vesicule pour penetrer dans le vitellus.” 
Holl (35) says; “Eine eigentümliche Form des Dotterkerns fand ich 
einige Male: sie besteht darin, daß derselbe in Form einer ringförmigen 
Masse um die Kernwand auftritt, und nach allen Seiten die gefärbten 
Strahlen in den ungefärbten Zelleib entsendet, und die Umwandlung des 
letzteren herbeiführt. Ist dies geschehen, so bildet sich eine neue, dichte 
«ich stark färbende Masse um die Kernwandung, welche neuerdings 
tiefer gefärbte Strahlen als früher allseitig entsendet und die Umwandlung 
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