TESTICLE-CELLS OF FUNDULUS 137 



together. In the cornea no pigment is present. If one studies 

 the point of transition between cornea and skin, one can see how 

 the mitochondria gradually take the place of the pigment-gran- 

 ules. This observation is interpreted by Prenant, apparently 

 not without reason, as indicating the transformation of chondrio- 

 somes into pigment and in the same sense could be interpreted 

 the conditions just described in" the excretory ducts of the fish- 

 testicle. 



The seminiferous cysts are reunited by thin sheets of connective 

 tissues containing blood-vessels and cells. Some of these are 

 conspicuous by their large size and by the presence of a great 

 number of bacilli-shaped chondrioconts (fig. 2) ; others contain 

 also granules which I am inclined to consider as secretion-prod- 

 ucts. In places where the connective tissue is somewhat more 

 abundant, for instance in such stellar spaces as appear between 

 the cross sections of the cysts, they usually build groups of two 

 or more elements. The nearest interpretation of these cells is 

 that they correspond to the interstitial cells of the ma nmalian 

 testicle. Supposing I were right, this would be the first men- 

 tion of them in fishes, or, as far as I know, the literature does 

 not contain any mention gf interstitial tissue in this class of 

 vertebrates: in fact Friedmann ('98) and Ganfini ('02) state 

 positively that they could not find it. 



The distal part of the cysts is occupied by cells which are 

 obviously the stem of the whole seminal lineage and as such 

 should be designated as spermatogonia. Since, as we shall see, 

 several generations of spermatogonia can be distinguished, I 

 would call these 'primary spermatogonia.' Their size is rela- 

 tively large (fig. 3, two cells on the top row and two cells at the 

 right). Each nucleus contains usually only one large, sharply 

 delimited, spherical block of chromatin-. The eventual occur- 

 rence of multiple nucleoli is often accompanied by the presence 

 of indentations (the process is just indicated in figure 3, in the 

 cell of the top row, to the right), which are suggestive of direct 

 division. Mitosis however was repeatedly observed (figs. 4 and 

 5). It would not be surprising if these indentations were indic- 

 ative of a process described as occurring in the spermatogonia of 



