Basis of Sex Determination 225 



7. The effects of the removal of the ovaries or 

 testes upon the development of secondary sexual 

 characters differ for different species. In insects the 

 secondary sexual characters are not altered by an 

 operative removal of the sexual glands as in the cater- 

 pillar, e, g.j Ocneria dispar, according to Oudemans. 

 This result has been invariably confirmed by all subse- 

 quent workers, especially by Meisenheimer. Crampton 

 grafted the heads of pupae of butterflies upon the bodies 

 of other specimens of the opposite sex, but the sexual 

 characters of the head remained imaltered. 



In vertebrates, however, there exists a distinct 

 influence of a secretion from the sexual glands upon the 

 development of certain of the secondary sexual char- 

 acters, which do not develop until sexual maturity. 

 In a way the observations on arrhenoidy and thelyidy 

 referred to above are indications of this influence. 



Bouin and Ancel had already suggested that the 

 sexual glands of mammals have two independent 

 constituents, the sexual cells and the interstitial tissue; 

 and that the latter tissue is responsible for the develop- 

 ment of the secondary sexual character. This has 

 been proved definitely by Steinach,^ who showed that 

 when young rats are castrated certain secondary 

 sexual characters are not fully developed. The seminal 

 vesicles and the prostate remain rudimentary and 



^Steinach, E., Zentralhl. f. Physiol., 1910, xxiv., 551; Arch. f. d.ges, 

 Physiol., 1912, cxliv., 72. 



