ORGANS OF INTERNAL SECRETION 307 



testes in fowls arrests the development of the comb and spurs 

 and other secondary male characters which are normally present 

 in the cock. Other instances of the effects of castration are 

 briefly referred to by Darwin.-' 



Secondary sexual characters, however, are not always 

 correlated with the essential organs of reproduction. For 

 example, castration in the horse does not arrest the develop- 

 ment of the withers — the gelding, in this respect, resembhng 

 the stalhon rather than the mare, in which the withers are lower.^ 



In Arthropods the correlation between the secondary sexual 

 characters and the generative glands appears to be far less close 

 than it is among Vertebrates. Thus, Oudemans ^ showed that 

 the removal of the testes from the male caterpillar of Ocneria 

 disfwr had no influence on the development of the secondary 

 male characters, these being normal. Kellogg * performed a 

 similar experiment on the caterpillar of the silkworm moth and 

 obtained a like result. Crampton ' grafted the heads of cater- 

 pillars of one sex upon the bodies of individuals of the opposite 

 sex, and found that the generative organs had no influence 

 upon the development of the secondary sexual characters of the 

 transplanted heads. Moreover, Meisenheimer * found that in 

 caterpillars artificially made hermaphrodite (by transplanting 

 ovaries into males or testes into females) the original males 

 always developed into butterflies with typical secondary male 

 characters in spite of the fact that hving ovaries were present, 

 while the original females always developed into normal female 

 butterflies. The sexual instincts were also unmodified by the 

 presence of the grafted gonads. 



In spider crabs attacked by Sacculina the gonads disappear, 



^ Darwin, loc. cit. Selheim {Beitrdge zur Oehurtshiilfe und Oyndk., ¥ol. i., 

 1898, and vol. ii., 1899), states that there is an increase in the size of the skull, 

 pelvis, and leg-bones in castrated cooks. 



^ Wallace, Farm Live-Stoch of Great Britain, 4th Edition, London, 1907, 



' Oudemans, " Falter aus Castriten Baupen," Zool. Jahrbilcher, vol. xii., 

 1899. 



' Kellogg, " Influence of the Primary Reproductive Organs on the Second- 

 ary Sexual Characters," Jour, of Exper. Zool., vol. i., 1904. 



5 Crampton, " An Experimental Study upon Lepidoptera," Arch. f. 

 Entwick.-Mechanik, vol. vii., 1898. 



' Meisenheimer, Experimentelle Studien zur Soma- und Oeschlechts- 

 Differenzierung, Part I., Jena, 1909. 



