LÉPIDOPTÉROLOGIE COMPAREE 475 



produce no female — a condition that has only been exceptionally 

 modified in the case, of the two middle crosses. 



Two of tiiem : 



P. pomonaria cf x Z. hïrtaria Q = hybrid hunii; 

 L. hirtaria cf x P. pomonaria Q = hybr. pilzii; 



yield the sexes in approximately equal numbers. 



Whilst two : 



/. zonaria çS y- P- pomonaria Q = hybr. langei; 

 I. zonaria (S x L. hirtaria Q = hybr. harrisoni; 



give an excess of females. 



Lastly, the only secondary hybrid bred up to the présent, i. e. 

 P. pomonaria cf x L. hybr. pUzii Ç) = hybr. brooksi. 

 yields spécimens hopelessly gynandromorphic. 



The problem as to why this state of affairs should hold at once 

 présents itself. It is perfectly clear that little or no absolute 

 évidence can be brought to prove this, or disprove that theory. 

 The dominance of male-ness in the hrst four, and the proportion 

 of females in the third group, suggest a simple Mendelian 

 explanation, but the only simple one based on Mendel's " Law " 

 contains a grave defect. However, it will be given in its proper 

 place. 



Let us consider the failure of females in the first four cases. 

 One is at once seized with the notion that, as /. zonaria takes 

 part in three of them, the failure must be due to the female of 

 that species. The only point of différence seen in that form, is 

 the exceptional size of the Ç.^^, which is greater in volume than 

 those of the other species, but why this différence should affect 

 the female sex only is difficult to see, and, fortunately, direct 

 évidence can be brought to prove that no such interférence with 



