114 
J. T. CUNNINGHAM. 
X), the germinal vesicle is very conspicuous ; it is coloured uni- 
formly pink, is of spheroidal form, and apparently homogeneous. 
The germinal spot is a brilliant deeply-stained spherical glo- 
bule, with a regular contour. It is situated near the periphery 
of the vesicle, and is surrounded by a spherical mass of sub- 
stance distinct from the rest of the vesicle. This envelope of 
the germinal spot is more deeply stained than the rest of the 
vesicle, and remains distinct throughout the changes of the 
latter. It is named by van Beneden the prothyalosoma, the 
rest of the vesicle being called the accessory portion. Nearly 
always in the accessory portion there are one or two formations 
similar to the prothyalosoma, each containing a “pseudo- 
nucleolus j” these disappear during the changes which the 
vesicle undergoes. 
The prothyalosoma projects slightly beyond the general 
surface of the germinal vesicle. Round the vesicle there is a 
distinct membrane : the layer within this occasionally shows 
minute granulations. In preparations obtained by treatment 
with nitric acid and borax-carmine the germinal spot appears 
not as a single body but as a group of small globules. The 
author believes that the germinal spot is always composed of 
two discs in close apposition, each disc consisting of four 
globules. The globules are connected by a substance with less 
affinity for staining substances than the globules themselves. 
In ova perfectly ripe for fertilization treated with alcohol 
and borax carmine, the nucleolus appears as a group of numerous 
globules in which no definite arrangement is seen. The acces- 
sory portion presents a punctated appearance, and the small 
granules to which this is due are arranged in rows resembling 
moniliform threads of protoplasm. These rows of granules are 
chiefly derived from the transformation of the membrane. 
Similar rows of granules connected by very fine threads are 
also to be seen in the prothyalosoma. 
In ova which are perfectly ripe, whether treated with nitric 
acid or alcohol, the spherical shape of the vesicle is deformed 
bv the intrusion of a homogeneous droplet on each side so that 
the vesicle appears in optical section in the form of a T. 
