313 



genesis Hie interstitium increases considerably in size. In it astrong 

 augmentation of the nnniber of" Lkydig's cells and of tlie blood- 

 vessels lias taken place. According to Couruier the testes of Stickle- 

 backs, caught ill winter, only contain a few inlei'slitiai cells here 

 and there. The spermatogenesis, which is very intensive in spring 

 till the end of March, has no intlnence on the development of the 

 secondary sex-characters. The latter occur not earlier than at the end 

 of April, siinnltaneonsly with the strong development of tlie inter- 

 stitial cells. As he, moreover, observes the same grannies in the 

 cells of IjEYDIG and in the bloodvessels, situated close to them, he 

 assumes that the hormones which influence the development of the 

 sex-characters are formed in the interstitial cells and pass from the 

 latter into the blood. In my o|)inion it might be that the granules, 

 observed by Courhier, are transmitted by the blood to the inter- 

 stitial cells. 



CouHRiER has also kept his fishes in water of 17° C. (1922^/ and 

 19226, p. 137) during a part of the winter. After two months and 

 a half the structure of the seminiferous tubules of these animals 

 resembles that of animals during breeding time i. e. they are entirely 

 filled witli spermatozoa and contain only a few spermatogonia, 

 spermatocytes and cells of Sehtot,i. Changes in the interstitium have 

 not occurred. Conse(iuently, the secondary sex-characters have not 

 developed in these animals. Courhier thinks, however (1922*/, in a 

 note), on the ground of experiments, which were in progress at that 

 time, that the interstitium would increase in size, when exposed 

 longer to a high temperature and that consequently the sex-characters 

 would also develop in these animals. 



I think I am justified to conclude from my investigations, de- 

 scribed above, that the correlation of interstitial cells and secondary 

 .sex-chaiacters is not so easy to establish. 



In the first place all testes of (rnsterosieus possess a more or less 

 large number of interstitial cells. These evidently do not cause the 

 development of the secondary sex-characters. Here I must especially 

 point to the male above described (N°. 6) of which the testes 

 contain a wide interstitium with many Leyuiu's cells and of which 

 the seminiforous tubules are entirely filled with spermatozoa. The 

 secondary sex-characters had not developed in this animal, however. 

 Among the testes of control-animals, caught in nature in winter, 

 I also found some of which the tubules almost exclusively contained 

 spermatozoa and of which the interstitium with numerous interstitial 

 cells is rather strongly developed. These animals, however, did not 

 show sex-characlers either. 



