178 J. DUESBERG. 



in close proximity to the nucleus, a differentiation of the cyto- 

 plasm (Figs. I, 2 and 8). This zone contains the centrioles of 

 the resting cell and is undoubtedly to be considered as an idio- 

 some. In contradistinction to what one observes in the seminal 

 cells, the idiosome of the interstitial cells is not sharply delimited 

 by a special cortical layer. It appears most clearly in material 

 fixed with Bouin's fluid or with any reagent containing osmic acid. 

 It is frequently found located in the nuclear depression, as 

 Ballowitz (1898, 1900) observed it, but not always so (for in- 

 stance, Fig. i). While two centrioles exist in the cells provided 

 with only one nucleus, I find, as did Winiwarter in human 

 material, that binucleated cells have four centrioles, and in some 

 cases these are obviously rod-shaped (Fig. 2). 



The extreme results obtained for the apparatus of Golgi by 

 the Ramon y Cajal method are illustrated in Figs. 3 and 4. 1 

 In the first, the apparatus appears as a dense reticulum, in the 

 second the reticulum is much looser. Normally, the apparatus 

 is concentrated at one pole of the nucleus; cases like the one 

 represented in Fig. 4, in which one or two branches of the net- 

 work extend to the opposite pole and surround the nucleus com- 

 pletely, are exceptional. The apparatus is found either in the 

 nuclear depression or in another place (Fig. 3). It behaves in 

 this respect like the idiosome, and consequently nothing definite 

 can be said concerning the topographical relationship of these 

 two bodies. Nothing, however, would seem to militate against 

 the existence of a close relationship such as has been established 

 for a large number of other cells (for literature, see Duesberg, 

 1914, 1919). Other investigations will probably help to solve 

 the problem, the present one being, to the best of my knowledge, 

 the first on the apparatus of Golgi in the interstitial cells of the 

 testicle. Concerning the interstitial cells of the ovary, we have 

 the data of Cattaneo (1914) and Kulesch (1914). 



While the interstitial cells of the opossum contain little fat, 

 it would not be correct to say, with Whitehead, that they contain 

 none at all. As a matter of fact, while the number of fat drop- 

 lets is usually small, it varies with each animal. In other mam- 



2 Another drawing of an interstitial cell in the testicle of the opossum, with the 

 apparatus of Golgi, will appear in another paper (1919, Fig. 34). 



