ON SOMATIC SEX-CHARACTERS 95 



rays destroy the spermatic cells of the testis in 

 Mammals, leaving the cells of Sertoli, the interstitial 

 tissue, nerves, and vessels uninjured. Tandler and 

 Gross ^ found that the antlers of roebuck were not 

 affected after the testes had been submitted to the 

 action of the rays, showing that the interstitial 

 cells were sufficient to maintain the normal condi- 

 tion of the antlers. Simmonds,^ however, found that 

 isolated seminal tubules remained, and regeneration 

 took place, and concludes that both spermatic cells 

 and interstitial cells take part in producing the testis 

 hormone. The conclusions of two other investi- 

 gators have an important bearing on this question — 

 namely, that of Miss Boring ^ that there is no inter- 

 stitial tissue in the bird's testis, and that of Miss 

 Lane-Claypon,^ that the interstitial cells of the ovary 

 arise from the germinal epithelium, and are perfectly 

 equipotential with those which form the ova and 

 Graafian follicles. It seems possible, although no 

 such suggestion has been made, that the interstitial 

 cells might either normally or exceptionally give 

 rise to ova and spermatocytes. The observations 

 of Seligmann and Shattock on the relation of sperma- 

 togenesis to the development of nuptial plumage in 

 drakes probably receive their explanation from the 

 above facts. Spermatogenesis is not the only 

 source of the testicular hormone : changes in the 

 secretory activity of the interstitial cells or sperma- 

 tocytes are sufficient to account for periodic de- 

 velopment of somatic sex-characters, and the same 

 reasoning applies to the antlers of stags. 



^ Wiener klinische WochenscJirift, 1907. 



2 Fortschr. a. d. 0. d. Rdntgenstr,^ xiv., 1909-10. 



3 Biol Ball, xxiii. 1912. * Proc. Roy. Soc, 1905. 



