OVARIAN OVUM OF MARSUPIALIA AND MONOTRP^MATA. 123 



both have been treated with the same reagents. And there is 

 an almost equal difference betvveeu the appearance of the con- 

 tents of a younj^ and of an old follicle in the same Marsupial 

 ovai'y (compare figs. 4 and 6). In the younger stages, when 

 the follicular contents are finely granular, and the ovum is not 

 yet isolated, the granulosa cells next to the central contents 

 frequently appear swollen and vesicular, unstained, and with 

 no distinct nuclei {fig. 4). Later there appears a distinct 

 intermediate layer between the central contents and the 

 granulosa. This layer is a network which seetns to be con- 

 tinuous with the granulosa cells peripherally, and the strands of 

 the contents centrally (see fig. 7). The intermediate netvtork 

 stains, and nuclei are common in it, apparently placed at the 

 nodal points, so that it probably represents the granulosa cells, 

 becoming stellate and arranged as a network, which again is 

 continuous into the central contents. The latter generally show 

 some slight distinction between the peripheral layer close to 

 the intermediate network and the central part. Since writing 

 the above, I have examined a fresh specimen, but unfortnnately 

 there were very few large follicles present. There was cer- 

 tainly some fluid present in the largest follicles, but the fol- 

 licular contents could be forced out entire, and apparently 

 surrounded by a wall, which may be the granulosa. I cannot 

 be sure that this condition persists in the ripe follicle. The 

 fluid is, as usual, albuminous. I could not detect the granules 

 covering a network in the fresh state, but this may be due to 

 the fact that the follicles were not ripe. I hope to work at the 

 subject again. 



The largest follicles seem to be about 2 mm. in their largest 

 diameter, but there is not much difference between the long 

 and short axes. In one follicle of about this size, the external 

 fibrous part of the tunica fibrosa had thinned away at the most 

 projecting pole (beneath which was the ovum), and it is there- 

 fore likely that the follicle was ripe. It is impossible to do 

 more than speculate as to whether any of the gelatinous ova- 

 rian covering of the ovum (in the follicle) clings to it as an 

 accessory layer after being received into the oviduct. The 



