20 PnOCEEDIXOS OF THE 



the inner spot (iipjier jiart only) can bo detected ^vitll a lens, bnt 

 in tlio rest it is altogether absent. There is the most gradual 

 transition from the male in which the inner spot is largest to the 

 one in which it is smallest and can barely be made out with a 

 good lens. The male parent (A) of the 1901 family is without 

 the spot. 



Seven males of the 1901 family are normal, while the eighth 

 possesses, in addition to the upper, a distinct lower section. 

 Although the inner spots are transitional in size from normal to 

 very small, none are so minute as to require the use of the lens. 

 The facts strongly suggest that the presence of the inner spot is 

 dominant and that the female parent (B) carried the factors of 

 the normal male. This interpretation is rendered almost certain 

 by the four males of the 1902 family, of whicli two are without 

 the spot and two with it. Of the latter, one is normal while the 

 other has the lower section as well as the upper, this lower section 

 being in fact better developed than in any other male in the whole 

 of Mr. Ijacot's material. 



C. Geographical Eaces or Subspecies. 



A large amount of excellent work for many years has been 

 devoted to the study of the differences by which a species is split 

 np into I'aces in various parts of its total geographical range. In 

 Lepidoptera these differences are sometimes large, sometimes so 

 small as to rest upon a slight change in the form or size of a 

 single marking or even the presence of a few coloured scales 

 requiring a lens for their detection. It has recently been argued 

 that geographical races when based on small differences are due 

 to some influence resident in the locality — acquired and not 

 hereditary. Thus Professor Pnnnett has suggested * that this 

 may be the interpretation of a certain small difference between 

 the Oriental and African fonns of Danaida chrysipims. During 

 the past few years I have endeaxoured to persuade naturalists to 

 breed thiu butterfly and test whetlier a high or low degree of 

 development of the character in question — a single spot in the 

 fore wing — is hereditary, and whether the local races will still 

 come true if bred in another country inhabited by another local 

 race of the same species. Up to the present I have not succeeded. 

 The butterfly is so very common that it is difficult to arouse 

 sufficient interest in it. Furthermore it is not always easy to 

 find naturalists who can breed butterflies successfully. But 

 evidence of another kind, yielded by the allied American Danaida 

 pJe.rlppvs {archi'pims), seems to me quite conclusive. Availing 

 itself of modern meajis of locomotion, the JN'orth American rnce of 

 this butterfly (other races of the same species exist in Centrnl and 

 South America) has during the past 70-80 years been gradually ex- 

 tending its rajige over the warmer parts of the world. Fortunately 



* "Mimicry in Butterflies," Cjiinbridge, 191"), pp. 132-134. Sec also 

 Bedrock, Oct. 101?, pp. 3()0-3Ul ; Apr. 1914, \^\^. 41-43. 



