6O2 THE STRUCTURE AND DEVELOPMENT 



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 

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

 noticed about the mammalian ovary, viz. that the more ad- 

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



By the stage seven days after birth the ovary has reached 

 a sufficiently advanced stage to answer the more important 

 question 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 

 condition 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 beautiful reticulate nuclei, with, as a rule, one more espe- 

 cially developed nucleolus, and smaller granular bodies. Their 

 diameter varies from about 0*028 to 0*04 mm. and that of their 

 nucleus from o - oi6 to o - O2 mm. The majority of these ova are 

 not provided with a follicular investment, but amongst them are 

 numerous small cells, clearly derived from the germinal epithe- 

 lium, which are destined to form the follicle (vide fig. 40 A and B). 

 In a few cases the follicles are completed, and are then formed 

 of very flattened spindle-shaped (in section) cells. In the ma- 

 jority of cases all the ova of each nest are quite distinct, and 

 each provided with a delicate vitelline membrane (fig. 40 A). 



