122 
J. T. CUNNINGHAM. 
Relation of the Ypsiliform figure to the Germinal 
V esicle. 
A comparison between figs. 2 and 4 shows what this relation 
is. The clear spherical body is the prothyalosoma, the 
chromatic globules are the germinal spot or nucleolus. The 
spheroidal masses at the sides of the figure are the vitelline 
elements seen at an earlier stage to push before them the walls 
of the germinal vesicle. The axial fibrils of the similar 
branches are formed in the substance of the prothyalosoma 
partly. The remaining portions of the figure arise from the 
transformation of the accessory portion of the germinal vesicle, 
and especially from its membrane. 
In this connection the author points out that it is doubtful 
whether nuclear membranes and nucleoli are always homolo- 
gous. He regards chromatin as a kind of fluid which is 
absorbed by the more solid achromatic substance. An achro- 
matic membrane is not equivalent to a chromatic one, and 
while in the ovum all the chromatin or nearly all is contained 
in the germinal spot, in an ordinary cell it is diffused through 
various parts of the nucleus. Hence he believes the germinal 
corpuscle is not homologous with the nucleolus of a cell. 
The polar stars of the figure appear early in the transformation 
of the vesicle, at first close to the prothyalosoma from which 
they afterwards separate. The author regards them as centres 
of attraction. The pseudonucleoli probably go to form 
achromatic fibrils. The prothyalosoma is at first covered by 
achromatic fibrils above, but these separate and it is then 
exposed. 
Formation of Polar Globule from Ypsiliform 
Figure. 
The figure passes gradually to the periphery of the ovum ; 
there is reason to believe that it reaches the surface at the pole 
opposite to that at which the micropyle existed, as in one case 
the spermatozoon was still attached to the oospermatic mem- 
