16 Studies in the Hybrid JMatoiunsie. IV 



in the zygotes by their maleness ; therefore females will appear as in 

 ordinary broods, although it appears feasible enough, and is to be ex- 

 pected in the long run that, with repeated experiments, these females 

 may, should the exact sex potential arise, be replaced by intersexes in 

 odd cases. And these theoretical deductions are exactly in accord with 

 the facts ; the use of inbred pomonaria and lapponaria did yield a small 

 percentage of females. 



We shall now proceed to discuss the persistent failure, up to the 

 present, to upset the unisexual state of affairs in broods obtained by 

 hybridising L. hirtaria male and N. zonm-ia female. It was laid down 

 that, with the phylogenetical divergence from hirtaria, an accompanying 

 decrease of the potential of the male sex determiners was encountered. 

 Clearly then tb begin with, pomonaria, and still more emphatically 

 lapponaria, should be inferior to hirtaria in such powers. Whence, 

 on inbreeding, both should fall much sooner to that level which fails 

 to destroy the power of that sex chromosome lodged in the (under 

 ordinary conditions) female-producing ova of JS'. zonaria. Thus females 

 should appear much sooner in these cases than with hirtaria, and, in- 

 ferentially, much more readily with lapponaria than with pomonaria. 

 Of the truth of the latter statement, experimental proof was readily 

 secured. From this argument it seems certain that if the inbreeding 

 of hirtaria be pursued far enough, ultimately the hirtaria male and 

 zonaria female cross will result in the production of a limited number 

 of females. 



The problem of the Single Female in the Cross between N. zonaria Female 

 and a (P. pomonaria J" xF. isabellae $ ) Male. 



The advent of the single female in this brood may suggest that it 

 is susceptible of explanation on the same, or similar, grounds to those 

 advanced to account for the few females reared in the P. pomonaria ^ 

 X N. zonaria % and P. lapponaria (^ x N. zonaria % hybrids ; this 

 cannot be so. The reduction of the potencies of the sex genes by 

 inbreeding plays no part in the matter, the male used being of hybrid 

 origin. In parentage this male was of wild blood on both sides, the 

 pomonaria male coming from Munich in Bavaria, and the isabellae female 

 having been bred from wild larvae taken at Innsbruck in the Tyrol. 

 This diverse nature of the parents was reflected in the offspring, for 

 the hybrid male was of enormous size, its wing-expanse being 33 mm. 

 as against 32 mm. for pomonaria and 31*5 mm. for isabellae. 



