455 
vesicle (Graafian follicle) is a modified part of the medullary cord. 
In fig. 1c we have a beautiful example of a vesicle, which is 
Fig. 4. 16 sections from a series of 80 (each of 10 u). 
merely a swollen part of a medullary cord. A rest of this cord is 
still seen attached to the vesicle. Though less clear the vesicle of 
fig. 3 shows such a rest. By these observations, I am convinced that 
a great number of atypical vesicles in the preparation, described 
here, originated owing to a proliferation of the epithelium in parts 
of the medullary cords. Afterwards those cells are vacuolised and 
a vesicle is formed. The remaining cells form a cumulus oophorus 
round the egg-cells, which originally occurred in the modified part 
of the medullary cord. As there are also groups of egg-cells, as 
reproduced in fig. 2, which must be looked upon as egg-balls, it is 
