1905.] the Interstitial Cells of the Ovary in the Rabbit. 36 



germinal cells, but I hope to show that the process is one of differentiation 

 and not of division. 



The protobroque cell is the type of the original germinal cell ; it is small, 

 generally oblong or oval, and contains a large nucleus. The nucleus shows 

 a number of chromatin masses of varying sizes, and the whole nuclear area 

 gives a general impression of granulation (represented by shading in the 

 figures (Plate 1, fig. 2 (a)). There are no chromatin filaments. 



The deutobroque cell is very much larger, and the nucleus has for the most 

 part a strikingly transparent aspect, the granular appearance noticed in the 

 protobroque cell being confined to the periphery of the nuclear area. The 

 chromatin is quite differently arranged ; there are one or two irregular 

 chromatin masses, and strands showing nodular enlargements where they 

 intersect. See fig. 2 (/). 



Sections of a young ovary very soon before or after birth show a large 

 number of cells whose nuclei exhibit every phase of transition between these 

 two varieties. These changes in the nucleus may be classed broadly into 

 three divisions : 



1. The chromatin masses become fewer and larger. 



2. There is considerable formation of chromatin strands. 



3. The granular appearance gradually passes away from the centre of the 

 nucleus towards the periphery, leaving the centre clear. 



Some of these changes are shown in fig. 2 (6), (c), (d), (e). In the first 

 stage the whole cell becomes rounder, as also the nucleus, and the chromatin 

 has begun to aggregate, and there are traces of strands passing away from the 

 masses. These features increase in intensity until there are only a few 

 chromatin masses, but the strands are passing between them and intersect in 

 parts. The granular appearance has begun to leave the centre, which is clear. 



A further process on these lines brings the cell into the typical deutobroque 

 condition. It would therefore seem that the change from the protobroque 

 type is accomplished by means of transformations in the nuclear area, 

 accompanied by a growth in size of the cell, and it is unnecessary to suppose, 

 under these circumstances, that mitosis is also a method of formation. The 

 protobroque and deutobroque cells are therefore all oogonia, either potential 

 or actual, the transition from the one class to the other being probably 

 accomplished by processes of nuclear differentiation. 



At this period in the life of the ovary there is no appearance which could 

 be characterised either as egg-tubules or egg-clusters; there are large 

 collections of epithelial cells bounded centrally by the mesoblast, which 

 presents the appearance of connective tissue, This tissue penetrates but 

 slightly into the region lying peripherally to the main central core, but careful 



