vn] THE CASE OF PAPILIO P0LYTE8 89 



females contain in addition a factor which we may 

 call Y. The function of the Y factor is to carry the 

 change made by the X factor a step further, and to 

 turn the A form of female into the H form. 7 is a 

 modifier of X, but unless X is present Y can produce 

 no effect. All the different individuals which are to be 

 found among P. polytes in Ceylon may be represented 

 as follows : — 



lixxYY 

 li XX Ty 

 lixxyy 

 liXxYY 

 liXxYy 

 li Xx yy 

 UXXYY 

 liXXYy 

 li XX yy 



a XX YY 

 ii XX Yy 

 a XX yy 



4$? 



ii Xx yy 



ff$? 



iiXxYY 

 ii Xx Yy 



iiXXYY 

 iiXXYy 



ii XX yy 



In this way is offered a simple explanation in terms 

 of three Mendelian factors which serves at once to 

 explain the various results of the breeding experiments, 

 and the fact that intermediates between the different 

 forms of female are not found. 



The only other experiments comparable with these 

 on P. polytes are some made by Jacobsen on Papilio 

 memnon in Java^. Here again there are three forms 

 of female, one of which, laomedon, is something like the 

 male, while the other two, agenor and achates, are 

 quite distinct. Of these three achates, unhke the male 

 and the other two females, is tailed, and resembles 



1 Tijdschr. voor Entomologie, vol. 53, 1909. A more accessible 

 account is given by de Meijere, Zeit. f. indukt. Abatamm. u. Vererbimga- 

 lehre. vol. 3, 1910. 



