64 GENETICS 



Some of both types of course have Y-chromosomes in place 

 of the X's, so that there are germs cells AY, AX, AAYY, 

 AAXY, and AAXX. Such germ cells when they unite pro- 

 duce many different chromosome combinations, some with 

 autosomes in pairs, others with autosomes in threes or even 

 in fours; and with different numbers of X's and Y's. Many 

 individuals having such combinations have been produced 

 and studied. This has given opportunity to determine the 

 effect of varying the numbers of sets of autosomes, as well 

 as of varying the X's and Y's. 



The more important different combinations, with the 

 nature of the individuals produced, are given in the follow- 

 ing list : 



V 



Here we find that while two X's normally give a female, 

 if they are combined with three sets of autosomes they do 

 not give a female, but an individual intermediate between 

 the male and female; an "intersex." It is clear therefore 

 that the autosomes influence sex, as well as do the X's. 

 Furthermore, it is not the absolute number of autosomes 

 present that gives a particular effect, but the number of sets 

 of autosomes in relation to the number of X's. Three sets 

 of autosomes with but two XX's gives an intersex, while 

 three sets of autosomes with three X's yields again a normal 

 female. The sex produced depends upon a balance between 

 the autosomes and the X's. When the number of sets of 

 autosomes equals the number of X's (whether two, three or 



