The Development of the Mole (Talpa Europea), 
the Ovarian Ovum, and Segmentation of the 
Ovum. 
By 
Walter Heape, M.A., 
Demonstrator of Animal Morphology in the University of Cambridge. 
With Plate XI. 
Toe Rive Ovarian Ovum. 
Tue position of the ripe ovarian ovum in the ovary is 
betrayed by the rounded semi-transparent Graafian follicle 
in which it lies, projecting prominently on the surface of the 
ovary. 
If an ovary containing such a follicle be held firmly with a 
pair of forceps on a slide, and the follicle be pricked with a 
needle, or better still, sharply gashed with the point of a fine 
scalpel, the ovum spirts out on to the slide together with a 
not inconsiderable amount of clear transparent fluid, the 
liquor folliculi. 
In accordance with the degree of ripeness of the ovum thus 
obtained it is more or less completely invested by a mass of 
epithelial cells, in the midst of which it lay in the discus 
proligerus within the follicle. 
These epithelial cells are radially arranged round the ovum 
(fig. 1). The cells of the innermost layer are more or less 
elongated and their inner end, tapering somewhat, rests upon 
a thick transparent membrane which surrounds the ovum, 
the so-called zona radiata (the zona pellucida of the older 
observers). 
VOL, XXVI.—NEW SER. M 
