CLIMATIC VARIETIES 169 



agree entirely with the intermediates of Brittany and the Loire. 

 Reciprocals are alike. Of F 2 I only succeeded in raising very 

 few and of those that I had (about 30) nearly all were intermediate 

 in character, though perhaps rather less uniform than Fi. One 

 family alone, containing only 4 specimens, had one egerides, 

 and three fulvous intermediates. As the case stands alone I 

 hesitate whether or not to suppose it due to some mistake. More- 

 over from Fi crossed back with the respective parental types I 

 had fairly long series, especially from Fi X the southern type, and 

 looking at these families I cannot see any clear evidence of segre- 

 gation. On the contrary, I think that though there are slight 

 irregularities, they would, taken as a whole, be classed as coming 

 between the intermediate type and the extreme form used as the 

 second parent. This at least is true when the second parent was 

 of the southern type. 



On this evidence I have regarded the case as one in which 

 there is no good evidence of segregation and as conforming most 

 nearly with the conventional view of gradual transition in re- 

 sponse to climatic influences. Such influence must however be 

 indirect; for I reared five generations of the northern type in 

 England, and these, though they included several abnormal- 

 looking specimens in the last generation and then died out, did 

 not show any noticeable change from the fulvous colour of the 

 wild type. Merrifield 8 also found that heat applied to pupae 

 of the northern type produced no approach to the southern 

 type. 



Looking at the facts now in the light of more experience it 

 seems to me just possible that the case may be one in which, as 

 in Nilson-Ehle's Wheats, the dominant differs from the re- 

 cessive in having two pairs of factors with similar effects. The 

 fulvous type for example may have two or more elements in 

 separate pairs which together produce the full effect, and the 

 intermediate may have one of these. If this were so, some 

 segregation should of course eventually be observable, but the 

 proportion of the various fulvous and fulvous-intermediate 

 individuals would be large, and the reappearance of actual repre- 



*Ent. Rec., V, 1894, p. 134. 



