428 F. M, BALFOUR. 



Round the completed follicle a very delicate membrana pro- 

 pria foUiculi appears to be present.^ 



The larger ova, with follicular epithelium^ measure about 

 0'04.' mm., and their nucleus about O'O^ mm., the smaller ones 

 about 0*023 mm., and their nucleus about 0"01-i mm. 



(£) Medium sized ova. — They are still without a trace of a fol- 

 licular epithelium, and present no special peculiarities. 



(3) The smaller cells ivith modified nuclei. — I have great 

 doubt as to what is the eventual fate of these cells. There appear 

 to be three possibilities. 



ia) That they become cells of the follicular epithelium ; ip) 

 that they develop in ova ; (c) that they are absorbed as a kind of 

 food by the developing ova. I am inclined to think that some of 

 these cells may have each of the above-mentioned destinations. 



(4) The cells lohich form, the follicle. — The only point to be 

 noticed about these is that they are smaller than the indifferent 

 cells of the germinal epithelium, from which they no doubt 

 originate by division. This fact has already been noticed by 

 Waldeyer. 



The isolated follicles at this stage are formed by ingrowths of 

 connective tissue cutting off fully formed follicles from a nest. 

 They only occur at the very innermost border of the germinal epi- 

 thelium. This is in accordance with what has so often been 

 noticed about the mammalian ovary, viz. that the more advanced 

 ova are to be met with in passing from without inwards. 



By the stage seven days after birth the ovary has reached a 

 sufhciently advanced stage to answer the more important ques- 

 tion I set myself to solve, nevertheless, partly to reconcile the 

 apparent discrepancy between my account and that of Dr. Foulis, 

 and partly to bring my description up to a better known condi- 

 tion of the ovary, I shall make a few remarks about some of the 

 succeeding stages. 



In a young rabbit about four weeks old the ovary is a very 

 beautiful object for the study of the nuclei, &c. 



The pseudo-epithelium is now formed of a single layer of 

 columnar cells, with comparatively scanty protoplasm. In it there 

 are present a not inconsiderable number of developing ova. 



A layer of connective tissue — the albuginea — is now present 

 below the pseudo-epithelium, which contains a few small nests with 

 very young permanent ova. The layer of medium sized nests 

 internal to the albuginea forms a very pretty object in well stained 

 sections, hardened in Kleinenberg^s picric acid. The ova in it 

 have all assumed the permanent form, and are provided with 



' Loc. cit., Waldeyer, p. 23, denies the existence of tliis membrane for 

 Mammalia. It certainly is not so conspicuous as in some other types, but 

 appears to me nevertheless to be always present. 



