OPERATION OF THE GENETIC SYSTEM 75 



of those materials. The different proportions of materials 

 result in diverse chemical processes that give the two dif- 

 ferent hormones, and thus result finally in individuals of 

 different sex. 



May Other Things Besides the Chromosomes 

 Influence or Determine Sex? 



We have gone into the matter of sex determination pri- 

 marily for the purpose of getting light on the method of 

 action of the chromosomes. We have seen that the nature 

 of the chromosomes present affects the chemical and physi- 

 ological processes of development, and in this way deter- 

 mines which sex shall be produced. 



This suggests certain other questions regarding sex that 

 it will be well to examine briefly. It is commonly said that 

 sex is determined by the X-chromosomes (a true statement 

 so far as it goes) ; and from this it has often been concluded 

 that sex cannot be determined in any other way. In partic- 

 ular it has been held that this excludes the possibility of the 

 determination of sex by particular environmental condi- 

 tions. 



This conclusion is however quite without justification. 

 The fact that chromosomes determine sex does not prevent 

 other things from determining it. The chromosomes de- 

 termine sex only in the sense that changing the chromosomes 

 alters the sex. We have already seen that changing other 

 things likewise alters sex. Changing the X-chromosomes 

 alters sex; changing the autosomes alters sex; changing the 

 germ glands present alters sex; changing the hormone pres- 

 ent alters sex. It will be worth while to enumerate various 

 different ways In which sex could be determined, in view of 

 our knowledge of the method of action of the chromosomes. 

 Some of the ways are known to be realized; others are not 

 as yet known to occur. 



