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



51 



of cells cut off, and these rows do not form continuous layers round the 

 ovary (vide fig. 5). 



About the twenty-third or twenty-fourth day, and in ovaries of later dates 

 of pregnancy, a somewhat striking feature about some of these cells is that 

 they are no longer mononucleated ; two nuclei are frequent, three quite 

 common, whilst in some cases there may be as many as six. These nuclei 

 are not massed together as in a giant cell, but lie separate in the cell 

 protoplasm. The latter is very much greater in amount than in an ordinary 

 interstitial cell, and is irregular in outline. The appearance of these 

 multinucleated cells suggests that they have been derived from the fusion of 

 the same number of interstitial cells as there are nuclei in the cell. It will 

 be remembered that van Beneden pointed out this appearance in the bat's 

 ovary, when he found in some cases as many as eleven nuclei, and he 

 suggested that possibly one of them grew at the expense of the others, whom 

 it used as food, or that one might become an ovum and the others the follicle cells. 



Examination of a large number of these cell masses shows that in many 

 cases there is undoubted atrophy of one or more of the nuclei going on. In 

 some there is a clear space where a nucleus might have been expected, in 

 others the nucleus stains very faintly or only in parts, whilst there is usually 

 one nucleus which stains intensely, especially in the iron hsematoxylin 

 specimens, and in which the staining, even after extreme differentiation, is 

 still so dark as to remove all possibility of tracing any nuclear structure. 

 This points to some difference of metabolic condition, and the conclusion 

 seems obvious that this nucleus is growing strong at the expense of the 

 others ; one is reminded of the protoplasmic masses described by Balfour in 

 the young ovary and to which reference has already been made in this paper. 

 Here we have a number of potential ova (for the fact has already been 

 emphasized that all interstitial cells being derived from the germinal 

 epithelium are potential ova) massed together, of which the nucleus of one 

 of them grows at the expense of the others, which it uses as food material ; 

 in the young ovary the end-product is a primordial ovum. In the pregnant 

 ovary the end-product is likewise a " primordial " ovum. The cells of these 

 aggregations are all quite clearly ordinary interstitial cells, and the surviving 

 cell is also an interstitial cell differing only in the intensity of its staining 

 reaction. 



It has I hope been conclusively shown, in the earlier part of this paper, 

 that the interstitial cells have all been derived from the cells of the germinal 

 epithelium, and have all passed through the deutobroque condition, and it 

 has been pointed out by v. Winiwarter that if there is to be ovogenesis 

 subsequent to the first great ovogenetic period, the cells which are to become 



E 2 



