222 RAYMOND PEARL AND H. M. PARSHLEY. 



may not the sex chromosomes be affected by these agencies 

 along with the rest of the germ cell to a sufficient degree to 

 modify their specific effect? As has recently been pointed out: 1 

 "There are two ways of looking at the relationship between sex 

 chromosomes and primary and secondary sexual characters on 

 the assumption already made that the differential factor is 

 essentially quantitative in nature. On the one hand it may be 

 assumed, as it has been in most discussions of the subject, that 

 the A'-chromatin acts in a positive way, if at all, in the deter- 

 mination of sex. On this view two 'doses' of A"-chromatin, in 

 some manner not fully understood, positively determine the 

 development of female characteristics. It has been argued that 

 since the female is primarily anabolic in tendency, as pointed out 

 many years ago by Geddes and Thomson, the determination of 

 the female sex by a 'plus' condition in respect of chromatin 

 may be explained on the assumption that A'-chromatin is a sort 

 of 'tropho-chromatin' in which reside the energy potentialities 

 of the organism. 



"There are two difficulties which confront this interpretation. 

 The first is that the female characters cannot be regarded as an 

 extension or intensification of those of the male. Rather the 

 contrary is true. The male almost universally represents a 

 higher degree of specialization and differentiation in development 

 than the female. Another difficulty is found in the phenomenon 

 of hermaphroditism. 



"I would suggest that both of these difficulties may be over- 

 come and all of the facts be better interpreted by assuming that 

 A'-chromatin is not a positive cause of sex differentiation but 

 rather is an inhibitor of the development of male sex characters. 

 It is a well-known fact that in the vertebrates, where the embry- 

 ology of the genital organs have been most carefully studied, 

 the male condition represents a more extended and advanced 

 degree or stage of development than the female. The system is 

 in every part homologous in male and female, but the latter 

 appears objectively to have been arrested in a development 

 which, without such arrest, would have led to the same result 



1 Pearl, R., in as yet unpublished lectures on the "Biology of Sex," delivered 

 before the Graduate School of Agriculture, Lansing, Michigan, July 1-6, 1912. 



