J. W. H. Harrison 69 



possible; the females, especially those of T. bistortata, are extremely 

 delicate. On the slightest provocation they develop a kind of paralysis 

 in the legs which effectively prevents their oviposition, and speedily ends 

 with their death. In my work all these obstacles were surmounted and 

 fertile ova, laid in fluffy masses in various nooks and crannies, duly 

 obtained. 



II. The Inheritance of Melanism within the limits of the 

 ; SPECIES Tephrosia crepuscularia. 



To render the experiments as comprehensive as possible two sets 

 were initiated. In both the melanism was brought into the crosses by 

 means of a Midland insect ; on the other hand, in one instance, the type 

 insects caged up were from Kent, and in the other case extracted non- 

 melanic moths chosen from the progeny (1) of a melanic female captured 

 near Birmingham and (2) of a wild type female from Delamere were 

 employed. The main purpose fulfilled in carrying out the work in this 

 duplicate form was to determine whether the ordinary Northern and 

 Midland form of T. crepuscularia which, in spite of its slightly darker 

 and more blurred appearance, one refers to the type and assumes to be 

 genetically equivalent to it, behaved as if it were so. 



(1) The crossing of Southern types with Northern melanics. 



From a couple of black Yorkshire females broods were reared which 

 resembled the parents, in spite of slight fluctuating variation, very 

 closely in colour. As they appeared they were transferred to separate 

 cages and allowed to pair indiscriminately. Ova were obtained in due 

 course, and from the various batches an equally random selection of 

 two hundred ova, derived from each of the original females, was made. 

 As before, imagines from both batches were successfully reared; since 

 none of them showed any signs of departure beyond the limits of fluctu- 

 ation of the parental and grandparental form, it was patent that both 

 broods as well as their grandparents were homozygous for melanism, 

 and that in each instance the original female had paired in nature with 

 a similarly homozygous male. 



Representatives of these were then mated with pale Kentish cre- 

 puscularia, and broods summarised in Table I bred. 



Obviously, from these figures we were justified in our assumption 

 that families A and B were homozygous for melanism, and, secondly, it 

 is manifest that in this species melanism is dominant. However, it 

 must be noted that some slight degree of fluctuating variation was 



