No. 2.] THE OOGENESIS OF BUFO LENTIGINOSUS. “ 425 
Rana are composed of a hyaline substance and appear much 
like nucleoli, although they cannot be extruded nucleoli since 
nucleoli never wander into the cytoplasm. Born discovered 
small oval bodies near the nucleus in the cytoplasm of the 
egg of Triton which he hesitates to call yolk-nuclei since 
they never appear granular. Bataillon describes and figures 
the division of a small body lying in the cytoplasm of the 
egg of Rana which he considers to be a large nucleolus which 
has passed out of the germinal vesicle. He states that this 
body ordinarily disappears when the yolk is formed, and 
that he once saw it transformed into pigment. 
Bodies similar to the vitelline bodies in the egg of Bufo have 
been found in the mammalian egg by von Winiwarter (94), 
Gurwitsch (36), and von Skrobansky (85). These bodies 
are present in the cytoplasm in addition to a granular yolk- 
nucleus. The latter structure, according to the researches of 
von Winiwarter and Gurwitsch, is homologous to the idio- 
zome in the sperm-cells. The figures given by von Skrobansky 
of rounded bodies in the egg of the guinea pig are very similar 
to those shown in Figs. 36-38. Von Skrobansky states that 
these bodies increase in number as the egg develops and that 
they have a tendency to form in groups of two, three, or more 
which are often surrounded by a clear area. As their appear- 
ance is coincident with the disappearance of the yolk-nucleus, 
he suggests that the substance of the yolk-nucleus becomes 
differentiated into these rounded bodies, although it is not im- 
possible that they are new differentiation products of the cyto- 
plasm. 
Small homogeneous bodies appearing like the vitelline bodies 
in the egg of Bufo have been found in the cytoplasm of the 
eggs of various arachnoids, myriapods, and vertebrates, and 
classed with large granular structures as yolk-nuclei. From 
the researches of Henneguy, Balbiani (3), and others, it is 
evident that the term yolk-nucleus has been used in a general 
way to cover a number of different structures in the cytoplasm, 
as the term nucleolus has been applied to a variety of struc- 
tures in the nucleus. 
