250 Genetical Studies in Moths 



My experience repeated that of Prout and Bacot' in their Acidalia 

 virgularia work ; to the very end a blend was obtained. So emphatic 

 was this persistency in blending and the absence of any hint of segrega- 

 tion that the only explanation possible is that based on permanent 

 gametic blending. This therefore agrees perfectly with what one sees 

 whenever the inheritance of melanism of a perfectly continuous type is 

 investigated, and contrasts violently with the uniform evidence of segre- 

 gation seen in cases of discontinuous melanism like that of Boarmia 

 consonaria. 



(d) Sex-linked Inheritance. 



Although I quite recognise the assumptions underlying the use of 

 the word " sex-linked " as applied to the particular type of inheritance 

 I am about to consider, in my opinion the use of Morgan's^ word is 

 preferable to that of " sex-limited " which covers, as Darwin intended, 

 phenomena quite different from these. 



That sex-linked inheritance of certain elements in wing-banding was 

 exhibited by the moth genus Oporahia was first indicated in 1914 when 

 I reared reciprocal crosses between Oporahia dilutata and 0. autumnata ; 

 it was then perceived that whereas the males partook of the wing- 

 markings of both species, the females, on the contrary, resembled the 

 female of the species supplying the male participating in the original 

 cross. In the case of the hybrid between dilutata female and autumnata 

 male this resemblance was perfect but unfortunately only one F-^ female 

 was bred and the matter was not proceeded with. Still worse was the 

 predicament in the reverse cross where the influence of the male was 

 not so perfect ; here the F^ females were devoid of ovaries. Further- 

 more, the back crosses involving both F^ males proved almost completely 

 unproductive. Very powerful barriers were therefore set to investiga- 

 tions employing these interspecific crosses. Knowing that such anomalies 

 in sex condition did not exist in crosses between 0. autumnata and 0. 

 filigrammaria exhaustive experiments were undertaken with these two 

 forms, but they proved utterly fruitless. 



Light, however, was thrown upon the subject in a very unlooked for 

 fashion by breeding results involving the Carpet-banded mutation of 

 0. autumnata which I shall call latifasciata. In this mutation the 

 whole of the central area between and including the two median bands 



1 Prout and Bacot, "On the Crossbreeding of Two Eaces of the Moth Acidalia 

 virgularia" Froc. Roy. Soc. London, Vol. lxxxi. Series B (1909). 



* Morgan, " Sex-limited and Sex-liniied Inheritance," Amer. Nat. Vol. xlviii. (1914). 



