144 THE entomologist's record. 



var. vibtirni, and faint traces of the chain of white medio-dorsal tufts were stir 

 present. In their last skin all the long hairs became dusky. Their heads varied, 

 but all showed mottling of red and indigo in varied proportions. 



Imagines of crosses. — Of the imagines I can say but little, chiefly 

 owing to my failure to rear more than a very few, and also on account 

 of the slight and inconstant diflerences between the different races. 

 (1) Of the moths of the cibiirni x iiieridiojtalis groups, I can detect 

 nothing different from either of the parent races. (2) I reared three 

 (J s and four J s of the cross between (? (jKercufi (English) and vicn'dio- 

 nalifi (Cannes), and, beyond that they are rather undersized, I think 

 they would be taken for English moths, the bands on forewings being 

 waved. Here, as with the larvfe, the English strain appears pre- 

 dominant. (3) I have moths of three different crosses, one parent 

 being i^icula. In these, the L. var. liicida strain is generally apparent, 

 even if faint. In the males the russet tint is present, although modi- 

 fied, and the narrowness of the stripe or band on the forewings at once 

 strikes one as being in contrast with that of I., var. nn'ridionalis or L. var. 

 vibunii. The orange border to the hindwings is deepened by a brownish tint, 

 and in all the specimens save one there is a narrow yellow stripe at the 

 junction of the border and the central area. This does not occur in any 

 L. var. sicula I have seen, and is evidently due to the Cannes strain. 



Perhaps the most remarkable feature of these cross-pairings, as 

 regards the larvje, is the different result obtained from the crossing 

 of two races occurring in the same geographical area, and of crossing 

 two races occurring in widely separated areas. In the latter case we 

 get a blending of colours, as with L. var, Dieridionalis and L. var. 

 callunae, on the other hand, we get not a blending, but a division of 

 the offspring into two moieties, one following each form without the pro- 

 duction of intermediate forms. Somewhat similar facts have, I 

 believe, been noted as regards crossing in the human race in regard to 

 the colour of hair and eyes. It seems possible that the opportunity 

 and probable frequency of intercrossing has led, through the action of 

 natural selection, possibly, in the case of these larvfe, owing to the inter- 

 mediate forms being less effectively protected than the types, to some 

 mechanism in the germ plasm of the races living in near proximity 

 that brings about the division instead of the blending, which occurs 

 from crosses between forms inhabiting separated areas. It is, how- 

 ever, difficult to see, in view of this explanation, why the moths 

 breed true instead of becoming merged into one race, having white- or 

 red-haired larv?e indifferently, even on the supposition that both forms 

 are equally well-protected. 



I have no wish to get entangled in a discussion as to what con- 

 stitutes a species, but the perfect fertility of the pairings between the 

 different races, and crosses of the races, that I have had, is in marked 

 contrast with the results obtained by crossing Tephrosia bistortata and 

 T. crepuscularia, as is also the fact that hybridising these species and 

 Smerinthm occllatiis and N. populi results in shortening the pupal 

 period, whereas cross-pairing the various races of L. qitercih tends to 

 lengthen it."- 



* It will be noticed in Mr. Warburg's paper (which is to follow this) that his 

 later experiments and more extensive material tend to modify this statement. 



