HEREDITY AND SEX 135 



tion, this having been completely (or almost completely) trans- 

 ferred from the individual cells of the body to the hormone- 

 secreting cells of the gonads. Thus sex reversal can be most 

 readily induced in mammals, because hormone production is 

 localised in organs which can be removed and transplanted. 

 The zygotic constitution originally called these organs into 

 being, but their independence having been once established, 

 their modes of action .can be investigated irrespectively of the 

 zygotic constitution. 



To the question what it is that the. sex enzymes — which 

 themselves depend upon the chromosome constitution— produce 

 as the end products of their activity, Goldschmidt answers, " the 

 hormones which are responsible for the modelling of definitive 

 sexual form." 



A further point on which both Goldschmidt and Lipschiitz 

 lay considerable stress is that the variability of intersexual 

 types is due to the differences in the quantitative relations 

 between the male and female hormones, these varying with the 

 passage of time. Thus sex-inversion will take place the earlier 

 the greater the amount of the heterosexual hormone (the second 

 one to act) above the normal, and the extent of the change is 

 the more pronounced the sooner the heterosexual transforma- 

 tion begins in the development of the individual. Moreover, 

 those organs which are differentiated very early in embryonic 

 development do not usually undergo heterosexual change, and 

 in the gypsy moth the gonads are the last organs to be affected. 



To the fm'ther question as to what factors are capable of 

 producing a quantitative disturbance of the hormonic activity 

 of the sex glands, no complete or satisfactory answer can yet 

 be given. It is known that tumours of the suprarenal bodies 

 may be the cause, and also that abnormal conditions in regard 

 to food and environment may apparently have the same result, 

 as with Champy's newts, while " parasitic castration " in 

 crustaceans and insects seems to supply other instances. But it 

 is impossible to formulate any general principle applicable to 

 all the known phenomena. There is, however, an accumulation 

 of evidence that the gonads (and even the peritoneal epithelium) 

 may contain neutral germinative elements which can develop 

 along the lines of either sex, if the appropriate stimuli are present 

 (Gatenby). It must, however, be emphasised that intersexuality 



