1905.] the Interstitial Cells of the Ovary in the Rabbit. 53 



young ovary has been given side by side with that in the adult, and does not 

 call for any special description.) This is a transition form from the interstitial 

 nucleus to the leptotenic stage in the process of ovogenesis, and appears to be 

 brought about by the breaking up of the nuclear chromatin into an immense 

 number of filaments. The arrangement of the chromatin in the interstitial 

 cells is, as a rule, discrete either in a rather loose reticulum or round the 

 edges, usually the former. 



The first change is therefore the formation of fine filaments. The leptotenic 

 stage of v. Winiwarter is brought about by the enlargement of the nuclear 

 area and the spreading out of the filaments over this increased space, thus 

 producing a looser arrangement which consists of fine filaments with a rather 

 nodular appearance where they intersect (fig. 6 (2)). This state would appear 

 to be a very fugitive one (as observed likewise by v. "Winiwarter), judging by 

 the rarity of its occurrence. It is quickly passed through, and the nucleus 

 enters upon the synaptenic condition (fig. 6 (3)). This stage occupies much 

 longer than the last, and a relatively large number of nuclei are found in this 

 condition, which has many modifications. The filaments at the leptotenic 

 stage are spread out over the nuclear area, whilst at the final synaptenic the 

 chromatin is massed into a lump at the side of the nucleus. All stages may 

 be traced both in the adult pregnant ovary and the young ovary, but only 

 the most characteristic phase is figured, namely, that where a very appre- 

 ciable amount of massing has already proceeded, the mass being connected to 

 the sides of the nucleus by a few very fine filaments. 



The massing completed, there seems to be a rearrangement of the 

 chromatin, and it becomes spread out again, but this time the filaments are 

 thicker. This is the pachytenic stage (fig. 6 (4)). The number of nuclei found 

 in this stage is less than in the synaptenic, but still there are a fair number 

 in various conditions. The filaments are so markedly thicker and more bulky 

 generally that it is impossible to confuse it in any way with the leptotenic 

 phase. The chromatin does not fill the nucleus quite so much as in the young 

 ovary, but I have found sections where this was more the case than in the 

 one figured : moreover in some the chromatin seems to have a more continuous 

 disposition than is here represented. 



The transition stage between the pachytenic and dictyate or final stage is 

 not, according to my observations, quite analogous to v. Winiwarter's, and I 

 rather hesitate to call it diplotenic, as the duality of the filaments is not well 

 marked (see fig. 6 (5)) ; the chromatin is still arranged in thick strands, and 

 there is some trace of nucleoli, whilst at the same time there are a very few 

 thinner nodulated strands, foreshadowing the condition called by v. Winiwarter 

 dictyate, and which represents that of the young ovum. 



