﻿32 THE BNTOMOLOGISI. 



all of the same type represented as 2 M. On fertilization we 

 should have two types of zygotes formed, one of the composition 

 ? ? M M, and therefore a melanic female, and the other <? ? 

 M N, and therefore male, and possibly showing diluted 

 melanism. Introduce now a female not bearing the melanic 

 factor. Its gametes would be ? N and ? N. Fertilization with 

 a melanic male, yielding gametes <? N and ? M, would give zy- 

 gotes of the composition <? ? N N, which are non-melanic males ; 

 and zygotes, represented as ? ? M N, which would be females 

 melanic or diluted according to the greater or less dominance of 

 the melanic factor. Such a procedure was adopted in the cross 

 dilutata ^ x autumnata $ . The female hybrid bore melanism, 

 and the male was without it ; results just as one would predict 

 from the above scheme. 



In the reverse cross we have autumnata males of the form 

 (3" $ N N, and dilutata females represented as ? ? M M taking 

 part ; these would yield in the former case the gametes ^ N 

 and ? N, and in the latter gametes all 2 M. Fertilization 

 then would give zygotes of the form <? ? M N and ? 2 M N, 

 i.e. both zygotes are heterozygous, as far as melanism is con- 

 cerned. This heterozygousness is probably shown by the 

 suffused and blurred out-of-focus effect in both sexes of hybrid 

 rungei, and again the actual results agree with the predicted 

 ones. 



Concisely, the results can be shown as follows : — 



(I) dilutata S X autumnata 2 



Composition (?2MNx 22NN 



gametes I ^ ^ Both 2 N 



Fj Non-melanic males More or less melanic females 



J 2 NN 2 2 MN 



(II) autumnata S x dilutata 2 



Composition <?2NNx 22 MM 



gametes] "? ^ All 2 M 



Fj More or less melanic males More or less melanic females 



^ 2 MN 2 2 MN 



I have undertaken experiments, within the limits of the 

 same species, to confirm the above views ; these are not yet 

 complete, but I can say that the results obtained are not 

 inconsistent with the views here propounded. 



Lastly, it is easy to see in the greater potency of autumnata 

 the usual experience one has in similar experiments, that the 

 phylogenetically older species has the greater effect on the 

 hybrid produced, and that autumnata is the older form I have 

 alreadv shown. 



