66 GENETICS 



by bringing out certain other relations that are found In the 

 observations above described, on the relations of chromo- 

 somes to sex. 



( 1 ) As before seen, changing the number of X's, when 

 the autosomes are left unchanged, changes the sex. Two 

 XX's produce a female, one X a male. 



(2) Thus the female XX contains everything that Is 

 necessary for producing a male. It differs in having "two 

 doses" of X in place of one. By removal at an early stage 

 of development of one of these "doses," it should be possible 

 to transform the female Into a male (see later, page 77). 



(3) The male, XY or XO, contains all the kinds of 

 materials required to produce a female. It contains X, as 

 does the female; but it has only "one dose" of X in place of 

 two. 



It should be possible therefore to convert the male into a 

 female if the single X-chromosome of the fertilized egg 

 could be caused to divide into two, while the other chromo- 

 somes remained undivided, thus giving an individual with 

 chromosomes AAXX. 



(4) Thus males and females do not differ at the beginning 

 by containing different kinds of materials. Both demon- 

 strably contain the same kinds of materials. The difference 

 lies in the fact that the female has two centers of growth 

 and multiplication for a certain material (X), while the 

 male has only one center of growth for that same material. 

 Such a difference Is commonly spoken of as a difference in 

 "balance" among the chromosomes. 



If this material (X) has a certain type of effect, the dif- 

 ference between a condition with two centers of action for 

 that material, and a condition with but one, might well make 

 a great difference to the chemical and physiological processes 

 occurring. In every cell, throughout life, the processes In 

 the female are such as result from the interaction of these 

 two centers with the other cell contents, while in every cell 



