HEREDITY AND SEX 127 



stag, the horns of the stag-horn beetle, and many other siieh 

 structures or pecuHarities. It was supposed that the female 

 exercised an aesthetic capacity in selecting her mate, thus favour- 

 ing the hereditary transmission by the male of those qualities 

 of form and beauty which pleased her fancy best. Moreover, 

 the combats between rival males for the possession of the female, 

 such as occur during the rutting season of the stag, would result 

 in the more vigorous males, and those with the best weapons 

 of offence, coming off victors, and so surviving to perpetuate these 

 characters in their young. 



Sex Reversal and Intersexuality. — Notwithstanding the fact 

 that the two sexes are ordinarily correlated with the chromosome 

 constitution it is apparent that imder certain circumstances the 

 latter may be overridden, and an animal may possess some or all 

 of the characteristics of one sex in conjunction with the chromo- 

 some constitution usually associated with the other. Thus an 

 animal may be a male and produce spermatozoa which are fully 

 capable of fertilising ova, and yet have two X-chromosomes in 

 the cells of the body. Moreover, as already stated, there is 

 evidence that all animals have in some degree the potentialities 

 of both sexes, and even among the higher vertebrates true 

 hermaphrodites are not unknown. It is evident, therefore, that 

 apart from the chromosome constitution there must be some 

 other mechanism upon which the sex of the individual depends. 



True hermaphroditism {i.e, the existence of testicular and 

 ovarian tissue within the same individual) in man is exceedingly 

 rare, but a few cases have been described (see Lipschiitz), and 

 of these Blair Bell's and Berblingler's are of special interest. In 

 each there was a marked change of sexual characters from female 

 to male, and an ovario-testis was found with Graafian follicles 

 and seminiferous tubules containing cells that were probably 

 spermatogonia, but no actual spermatozoa.^ Menstruation took 

 place before the reversal set in, and reciu:red normally for a few 

 years, after which it stopped. In these and other instances 

 (in many of which so far as recorded the hermaphroditism did not 

 extend to the gonads) there were changes in the external characters 

 as well as in the psychology. Thus in Blair Bell's case, hair 

 grew on the face and other parts of the body, and the clitoris 



^ These individuals, therefore, differed from functional hermaphrodites 

 such as we find occurring normally in many invertebrates. 



