134 INTRODUCTION TO SEXUAL PHYSIOLOGY 



In insects the gonads exercise no influence over the secondary 

 sexual characters, or even over the sexual instincts. This is 

 explained by Goldschmidt on the assumption that the production 

 of the sex hormones in these animals is not localised in special 

 organs, but takes place within all the cells of the body. It is 

 impossible, therefore, to obtain " Hormonic Intersexuality " in 

 insects, but " Zygotic Intersexuality " can be obtained as Gold- 

 schmidt has demonstrated in an extensive and elaborate in- 

 vestigation with cross-breeding the gypsy moth (Lymantria 

 dispar). In crossing a male of a European variety with a 

 Japanese female the first generation of crosses (or F^'s) are either 

 males or intersexual females. In the converse cross, all the 

 Fi's are normal males or normal females, but the Fg's are inter- 

 sexes. Goldschmidt has elaborated the idea of " strong " and 

 " weak " races. Thus a " strong " male mated with a " weak " 

 female will produce female offspring, but these w^ill show 

 modification towards tlie male condition, while the males will 

 be normal. Goldschmidt explains these results on the ground 

 that though the female-producing factor is normally stronger 

 than one X, a male factor from a " strong " race has a quicker 

 action than normal, and in time overpowers the female factor 

 with the result that a moth which has started as a female after- 

 wards develops certain male characters. Two X's, whether from 

 " strong " or " weak " races, produce the usual result, i.e. a 

 normal male (see p. 136, footnote). There are various degrees of 

 strength in the different races of gypsy moth, and the sexual 

 characteristics of the offspring depend upon what crosses are made. 

 In this way, a complete scale of intersexuality may be obtained. 



Birds are supposed in some degree to resemble insects in 

 that all the cells may contain both sexual formative substances. 

 In this way Goldschmidt interprets " gynandromorphism," 

 which occurs in both insects and birds. It is a condition in which 

 one side of the body has male characteristics and the other female, 

 the actual gonads also being often different so that the animals 

 are hermaphrodite. Poll's bullfinch and Weber's chaffinch are 

 well-known examples of bilateral gynandromorphism. Anterio- 

 posterior gynandromorphs have also been described, as in the 

 case of Bond's pheasant. 



Gynandromorphism cannot occur in mammals which represent 

 the last stage in the centralisation of the control of sex differentia- 



