260 Genetical Studies in Moths 



evidently correlated with the advent of a previously unknown imaginal 

 form which we shall discuss below. 



The larvae fed up normally and the pupae passed the summer safely 

 to yield a total of 86 imagines in autumn. These divided themselves 

 sharply into two sections, one composed of 27 males and 8 females being 

 precisely like their parents and therefore intermediate between true 

 autumnata and filigrammaria. This intermediate portion needs no 

 description and would not be further mentioned except to indicate that 

 it included one teratological female in which the left antenna was dupli- 

 cated. The other division composed of 24 males and 27 females was 

 wholly dissimilar; the individuals in it resembled neither their parents 

 nor, save in a manner common to the genus, did they approach the pure 

 species from which they had been derived. Moreover, although fluctuating 

 variation was present, still the impression one gained from the series was 

 one of complete uniformity. In view of their peculiarities therefore they 

 are worthy of a detailed description. 



The ground colour is of an almost pure white interspersed with a 

 few grey scales ; in two cases, one male strongly and one female weakly, 

 this is sufifused with a smoky tinge. 'Across this ground passes a band 

 differing widely in its build from that seen either in autumnata or fili- 

 grammaria — or even in dilutata. In ordinary pure species we have two 

 central bands, each of which is composed of two lines more or less parallel, 

 connected up by a suffusion varying in depth with the species and with 

 the genetical type of the race within the species. In the filigrammaria 

 female employed to produce the F^ generation, the shading was so deep 

 as to differ in no wise in intensity from that of the bounding lines; on 

 the other hand, in the autumnata parent this was very much less concen- 

 trated. As we have seen the F^, F^, and a portion of the ^3 lots were 

 intermediate in this respect. The band in the central area of the aber- 

 rant section is wholly distinct in design from any of these. Almost in 

 every case the bounding lines of the bars in which they occur are distinct 

 enough, although they give one a sense of being out of focus, but, what is 

 more important, the outer member of the inner band is obsolete in all 

 cases ; in others (all males) the same fate has befallen the inner one of 

 the outer band. In the latter event, the two existing lines tend to be 

 united by a brownish suffusion and in all the examples the two normal 

 outer ones show the same trend. Occasionally (to be exact in half a 

 dozen examples), the line proper to the outer band moves toward the 

 base of the wing and becomes central ; here, likewise, a brownish suffusion 

 tends to occupy the whole of the central wing area. Another curious 



