242 Mr. E. A. S chafer. On Immature Ovarian Ovum [Mar. 18, 



accumulation of liquor folliculi. In the latter case the matrix above- 

 mentioned is absent, and the macula is represented by a number (a 

 dozen or so) of globules of varying size which appear to lie loose 

 within the germinal vesicle (fig. 23, b). An intra- vesicular network is 

 sometimes present, and serves to unite the granules of the macula, 

 which are then few in number and individually larger (figs. 21 and 

 22). It is possible that the homogeneous matrix above described may 

 represent the remains of such a network, the filaments of which have 

 shrunk up into a mass on contact with the hardening reagent ; but if 

 we are to assume this for some cases, it is difficult to understand why 

 it should not take place in every case. 



Germinal Vesicle. — With the exception of the germinal spot or spots, 

 and the intra- vesicular network when present, the contents of the ger- 

 minal vesicle are perfectly clear and do not become stained to any 

 appreciable extent. The vesicle is either completely spherical in shape 

 or it may present one or more bulgings (fig. 18), and these bulgings 

 are frequently turned towards the nuclei presently to be described as 

 making their appearance in the peripheral layer of the vitellus. In 

 some of the sections the wall of the germinal vesicle seems to be defi- 

 cient for a small extent (fig. 14, v. g.)< as if to permit of an admixture 

 of its contents with the yolk ; but this appearance may be due to the 

 wall having become so thinned as to be imperceptible. In some of the 

 smallest Graafian follicles two germinal vesicles are seen within one 

 ovum (fig. 26). It is possible that one of these may afterwards dis- 

 appear, i.e., that the follicle is really a nest, containing two fused primi- 

 tive ova ; or, on the other hand, that the follicle and ovum are about 

 to divide. 



Vitellus. — In small ovarian ova the vitellus, as in the corresponding 

 ova of the bird, is in the form of a comparatively open network of 

 anastomosing filaments (figs. 21, 22). These tend to become collected 

 more thickly together immediately around the germinal vesicle, and 

 also at the periphery of the vitellus. In larger ova a network is no 

 longer recognisable, but the vitellus acquires a uniformly granular 

 aspect, with generally a number of larger and more distinct granules 

 imbedded in it. In maturing ova the vitelline granules are chiefly 

 collected immediately in contact with the inner surface of the zona 

 pellucida, but are also distributed throughout the whole vitellus, dis- 

 posed, it has sometimes appeared to me, in closely anastomosing tracts, 

 leaving clear intervals between. 



The zona pellucida of the rabbit's ovum is late in becoming formed. 

 Even when the epithelium in the Graafian follicle is composed of two 

 layers of well-marked columnar cells, it is still thin and the radiating 

 pores cannot be detected in it. In later stages of growth the pores are 

 distinct enough, and they often appear to be occupied by minute 

 granules which are like the vitelline granules on the one hand, and, on 



