REPRODUCTION AND SEX 465 



ingly during the twentieth century. Moreover, there can now be 

 no sufficiently clear understanding of the phenomena of sex apart 

 from what we may call the "gonadial hormones". 



In the first instance the essential reproductive organs should not 

 be called "glands", as has long been the custom, but rather "gonads", 

 for their primary function is the production and liberation of egg- 

 cells or sperm-cells ; and ' cell-multiplication is not a glandular 

 function. Yet the old name "reproductive glands" is more accurate 

 than the critics of the usage knew, for it has been shown that the 

 reproductive organs of Vertebrate animals contain endocrinal tissue 

 which produces "hormones". These pass into the blood-stream and 

 are of profound importance in connection with sex and reproduction. 



Male Organs. — In very varied degree in different types there is 

 in the testis a kind of tissue (first noticed by Leydig in 1850) which 

 is usually called "interstitial". From the seasonal variations in the 

 amount of this interstitial tissue, and from other Hues of evidence, 



Forms of Abdomen in a Crab (Pachygrapsus), castrated by a parasitic Crus- 

 tacean. After Geoffrey Smith. A, the normal abdomen of the female; 

 B, the normal abdomen of the male; C, the abdomen of the parasitised 

 male, approximating to the female type. 



it is highly probable, if not certain, that it produces the specific 

 testicular "autacoid" or hormone. 



From ancient times it has been known that removal of the male 

 reproductive organs in early life is followed by the repression of 

 the man's normal masculine characters, such as beard, larger and 

 deeper-toned larynx, and stronger bones. Castration in later life 

 may be followed by retrogression in masculine characters and by 

 the putting on of fat. 



Similarly, in other organisms, the removal of the testes prevents 

 or checks the development of the stag's antlers, the cock's spurs, the 

 swollen first finger of the male frog, and so with many other 

 secondary sex-characters. Moreover, the implantation of testes or 

 pieces of testes from another animal, even when inserted in quite 

 irrelevant regions of the body, may have the result of counteracting 

 the check that had set in. Thus Nussbaum found that a castrated 

 frog, which in ordinary circumstances would not develop any 

 sweUing on the first finger, did grow the normal pad, used in the 

 sex-embrace, when pieces of testes from another frog were grafted 

 into the dorsal lymph-sac. 



VOL. I HH 



