88 THE CASE OF PAPILIO POLYTES [ch. 



Iixx. The family from the second wild H female con- 

 tained 26 H and 7 M females; i.e. the ratio in which 

 these two forms appeared was not far from 3:1. 

 Hence the wild female was probably UXx and her 

 husband IiXx. If this were so some of the 26 $$ 

 should receive the X factor from both parents and 

 consequently be IiXX in constitution. This was 

 almost certainly so in the case of the single male in 

 this brood tested by mating with an M female from 

 the other brood. All of his 12 daughters were of the 

 H form, as should have been the case had his con- 

 stitution been IiXX. Supposing this to be so, all his 

 offspring, of both sexes, must be heterozygous for X. 

 Consequently any pair mated together should give 

 both H and M females in the ratio of three of the 

 former to one of the latter. In Mr Fryer's experiment 

 two males and two females chosen at random were 

 mated together. In the one case six H and one M 

 female were produced, in the other ten H and two M 

 females. As was expected both classes of female 

 appeared, and the looked-for ratio of three H to one M 

 was, in view of the smallness of the numbers, not 

 departed from widely in either instance. 



In the experiments selected as an illustration, the 

 mimetic females happen to be all of the H form. In 

 other experiments, however, both the H form and the 

 A form occurred. As the result of his experiments 

 Mr Fryer came to the conclusion that here again the 

 difference is one of a single hereditary factor. All 

 mimetic females contain the X factor, but the H 



