494 I IFE : OUTLINES OF GENERAL BIOLOGY 



disappear in the "atavism" that sometimes follows the crossing of 

 widely separated races. 



According to Kammerer, sex-characters have arisen phylogeneti- 

 cally, like species-characters, by direct and by functional adaptation. 

 They may Jiave begun in both sexes and have become subsequently 

 specialised in one (usually the male) — and this is probably true, on 

 the average, of the older characters. Or they may have begun in 

 one sex (usually the male) in response to peculiar conditions of life — 

 and this is probably true, on the average, of the later acquisitions. 



Sex differences, whether arising directly (environmentally im- 

 pressed on the passive organism) or indirectly (functionally estab- 

 lished by the active organism), become hereditary characters along 

 with the rest of the organisation. What were primarily common to 

 both sexes may be restricted to one; and what were primarily 

 restricted to one may become common to both; and there has 

 probably been a continual flux of sex attributes, the gonadial and 

 genital least, the extra-genital most. So far Kammerer's chief 

 conclusions. 



Illustrative Facts. — Kammerer bases his conclusions, for the 

 most part, on the results of recent experimental work. Let us take 

 a few illustrations from his .scholarly survey. The castration of 

 young mammals often leads to a lengthening of the long bones, to 

 a lessening of muscular development, to fattening, to inhibition of 

 brain development, and to suppression of sex-characters such as 

 antlers. The castrated female may show an activation of latent 

 masculine characters, but in the crabs castrated by Sacculina and 

 other crustacean parasites the males put on feminine characters. 

 In certain instances, as Tandler has clearly shown, what is developed 

 after castration tends towards the more primitive condition, to 

 what, in some cases, was probably common to both sexes. A doe 

 with antlers, a bearded woman, and a hen with cock's feathers may 

 illustrate this. In the case of caterpillars, whose sex is determined 

 before they leave the egg, no effect at all is produced by castration. 

 In parasitised irale crabs, what hapjx^ns, according to Geoffrey 

 Smith, is a change of the metabolism to feminine and female lines. 

 In Inachus the parasitised male crab develops egg-carrying ab- 

 dominal limbs like tho.se of a female, and even produces eggs. But 

 in this case the putting on of the external feminine characters 

 precedes the appearance of the ovaries. 



In some cases, such as the crests of male newts and the swollen 

 "thumb" pads of male frogs, regeneration does not occur unless the 

 gonads are present. In other cases, the regeneration of sex-char- 

 acters may take place in the absence of the gonads, or in the presence 

 of tho.se of the opposite sex. The influence of the gonads on re- 

 growth is at most quantitative, not qualitative. 



The consequences of the loss of reproductive organs can be 



