THE RIPE OVARIAN OVUM. 215 



produced into a kind of fold, forming a rim which rested on the 

 surface of the yolk. 



In neither of my specimens is the cavity in the upper part 

 of the membrane filled by the contents ; and the upper part of 

 the membrane is so folded and creased that sections through 

 almost any portion of it pass through the folds. The regularity 

 of the surface of the yolk is not broken by the germinal vesicle, 

 and the yolk around exhibits not the slightest signs of displace- 

 ment. In the germinal vesicle figured the contents are some- 

 what irregular in shape ; but in my other specimen they form a 

 regular mass concave above and convex below. In both cases 

 they rest on the yolk, and the floor of the yolk is exactly moulded 

 to suit the surface of the contents of the germinal vesicle. The 

 contents have a granular aspect, but differ in constitution from 

 the surrounding yolk. Each germinal vesicle measured about 

 one-fiftieth of an inch in diameter. 



It does not appear to me possible to suppose that the pecu- 

 liar appearances which I have drawn and described are to be 

 looked upon as artificial products either of the chromic acid, in 

 which the ova were hardened, or of the instrument with which 

 sections of them were made. It is hardly conceivable that 

 chromic acid could cause a rupture of the membrane and the 

 ejection of the contents of the vesicle. At the same time the 

 uniformity of the appearances in the different sections, the regu- 

 larity of the whole outline of the egg, and the absence of any 

 signs of disturbance in the yolk, render it impossible to believe 

 that the structures described are due to faults of manipulation 

 during or before the cutting of the sections. 



We can only therefore conclude that they represent the real 

 state of the germinal vesicle at this period. No doubt they 

 alone do not supply a sufficient basis for any firm conclusions 

 as to the fate of the germinal vesicle. Still, if they cannot 

 sustain, they unquestionably support certain views. The natural 

 interpretation of them is that the membrane of the germinal 

 vesicle is in the act of commencing to atrophy, preparatory to 

 being extruded from the egg, while the contents of the germinal 

 vesicle are about to be absorbed. 



In favour of the extrusion of the membrane rather than its 

 absorption are the following features, 



