THE OVA AND OVARY IN MAN AND OTHER MAMMALIA. 207 



not reach the stage of primordial ova, many of them abort 

 and disappear, and perhaps furnish a pabulum for the more 

 vigorous and healthy ones. 



In the ovary of a puppy at birth, one sees, in a beautiful 

 manner, the egg clusters under the germ epithelium in all 

 stages of development. Some of the clusters appear to con- 

 sist entirely of large primordial ova, while in others we can 

 trace the growth of the germ epithelial corpuscles into ova, 

 and immediately under the germ epithelium are little groups 

 of corpuscles in the act of being included in meshes of the 

 stroma. 



In following the further development of the ovary and ova, 

 we notice that around each egg cluster is a well-marked 

 capsule or mesh of vascular connective tissue. This con- 

 nective tissue consists almost entirely of fusiform corpuscles 

 and young blood-vessels. Just as at first, when delicate pro- 

 cesses of the young stroma grew upwards among the ordinary 

 germ epithelial corpuscles to include them in meshes, so now 

 delicate processes of the young connective tissue with blood- 

 vessels proceed from the walls of these meshes, and insinuate 

 themselves in among the developing corpuscles in each egg 

 cluster. As these processes thicken, the primordial ova 

 gradually become separated from each other, and at last each 

 is included in its own mesh or capsule of the stroma. 



These single egg- containing meshes or capsules are the 

 primordial follicles. 



This formation of young Graafian follicles takes place in 

 the egg clusters in all parts of the ovary, and at the same 

 time new egg clusters are being formed under the germ 

 epithelium in the manner described. In the ovary of a 

 seven and a half months' human foetus we find many newly 

 formed egg clusters immediately under the germ epithelium, 

 but below these, earlier formed egg clusters are in various 

 stages of alteration into single egg-containing follicles, while 

 deeper still we find a great number of young follicles all 

 produced from the first-formed clusters in the way we have 

 described (fig. 6). 



In the first-formed Graafian follicles, which are situated 

 most deeply in the stroma of the ovary, the young ova are of 

 large size, and we are at once struck by the fact that the 

 germinal vesicles in all are about the same size, although 

 the protoplasm around them may vary considerably in 

 quantity. 



In each young Graafian follicle the ovum fits tightly ; it 

 occupies the whole cavity of the follicle ; there is no space 

 between it and the wall (fig. 6, m, m, m). The mesh of 



