MATURATION AND FECUNDATION OF THE OVUM. 115 
The result then of the author’s study of the germinal vesicle 
before fecundation is as follows. 
Before the ovum is quite mature, that is to say, some little 
time before it has reached the upper part of the uterus, the 
vesicle is spherical and bounded by a thin achromatic mem- 
brane. As maturation progresses traces of a spindle of achro- 
matic fibrils are observed in the neighbourhood of the germinal 
spot; the fibrils are situated in the prothyalosoma, and are 
continuous with the chromatic discs of the spot. Nothing is 
to be seen resembling the convoluted chromatic filaments which 
appear in nuclei about to divide. The action of picro-carmine 
shows that chromatin is diffused to a slight extent throughout 
the vesicle. The pseudo-nucleoli behave towards staining 
fluids somewhat otherwise than the germinal spot. The 
germinal spot is in contact with the interior of the membrane 
of the vesicle. The accessory portion is composed of a denser 
substance next to the membrane and an internal more fluid part. 
Towards the time of the entrance of the spermatozoon some of 
the fluid contents passes out from the vesicle, and it therefore 
loses its rotundity and becomes smaller. Gradually both the 
membrane and the cortical layer of the accessory portion resolve 
themselves into delicate moniliform threads similar to those of 
the protoplasm of the vitellus. A similar change takes place in 
the substance of the prothyalosoma, but a little later. The vesi- 
cle is altered in shape by the intrusion of vitelline elements, and 
appears T shaped. This is the whole extent of the changes 
which take place before the entrance of the spermatozoon (see 
fig. 2, PL X. Into the ovum represented a spermatozoon has 
already penetrated; but the condition of the germinal vesicle 
shown may be reached before the contact of^the male element). 
The author gives some details concerning the ova of unfer- 
tilized females, but he says nothing about the formation of polar 
globules in such ova which is the most interesting point. 
Spermatozoa in the Uterus. — Spermatozoa are found 
in numbers in all parts of the uterine epithelium ; but they 
occur in greatest abundance in the upper extremity of the tube 
where the ova first meet with them. Since the uterus is dis- 
