6 Studies in the Hyhrid Bistoninae. lY 



(3) Hexes in the ordinary numbers, hut no ova ever deposited. 



Poecilopsis lapponaria female x Lycia hirtaria male. 



(4) Cross reproducing the main features of the last section but, in 

 addition, occasional intersexes appear. 



P. lapponaria female x Poecilopsis pomonaria male. 



(5) Grosses yielding males and intersexes. 



P. rachelae female x Lycia hirtaria male. 



Nyssia zonaria female x Poecilopsis rachelae male. 



(6) Crosses which, when under normal conditions, yield males only. 



Nyssia zonaria female x Lycia hirtaria male. 



N. graecaria female x L. hirtaria male, 



N. zonaria female x Poecilopsis pomonaria male. 



N. zonaria female x P. isabellae male. 



N. zonaria female x P. lapponaria male. 



The circumstances outlined in the first two paragraphs are quite 

 consonant with one's expectations in the study of hybrids; nor are 

 those recorded in the third paragraph a matter for surprise, for they are 

 a natural corollary to those preceding them. But one was quite unpre- 

 pared for the occurrences mentioned in the last three. 



In searching for a plausible interpretation of these facts, so utterly 

 unexpected, and so absolutely, on the face of the matter, at variance 

 with one's preconceived notions obtained from the Mendelian theory 

 of sex, let us see if we can correlate any further facts with observed 

 phenomena. 



Careful examination of the species makes it plain that whenever 

 the broods are abnormal the female is almost invariably provided by 

 Nyssia zonaria ; if it is not, and this occurs in two cases only, then the 

 female is that of P. lapponaria, the species from which N. zonaria is 

 evolved, or of N. graecaria, a form derived from it. On the other hand, 

 the male is uniformly that of a phylogenetically older insect than the 

 female. Furthermore, referring only to the anomalous families, the 

 nearer the genetic connection between the species concerned, the fewer 

 the number of aberrant intersexes making their appearance. 



Obviously, in the reciprocal crosses, in which no sex-weakening is 

 developed, the cross is, of necessity, between a phylogenetically older 

 female and a younger male. 



As has been demonstrated in Doncaster's work on sex-limited 

 inheritance in Abraxas grossulariata and in my own on Oporabia 



