( 448 ) 



oftbe individuals belong to the varietalform. A lllower degrees of localised variation 

 may be termed " localised aberration " (ab. loc. = aberrritio alictiim loci).* 



We have already referred to some observations which show that localised 

 divergent development is going on under onr eyes. There are certainly species 

 which are at present stationary, and perhaps have been so for a long time ; but so 

 much is certain that nearly all the si)ec.ies which have a wider distribution (except 

 a number of " globe-trotters ") exhibit some kind of local variation, and that, there- 

 fore, since local variation is the beginning of the divarication of a species into more 

 species, the more widely distributed species are at the present period actually in 

 a state of divergent development. We have examined a great many Lepidoptera, 

 both butterflies and moths, in regard to this question, and find tiiat tliere arc very 

 few species which are not split up into geographical races, although the diiferences 

 between the subspecies are often extremely minute. The degree of divergency 

 depends especially on the sensibility of the species in respect to the transmuting 

 factors, and on the degree of isolation and intensity of the latter, as well as on the 

 degree of geographical isolation. Wingless animals, and plants without means of 

 dispersal, are generally more easUy affected and on smaller areas than animals and 

 plants with good means of dispersal. Wingless beetles, for example, such as 

 Carabus, vary enormously according to locality; in the Alps, for instance, there 

 are a great many subspecies of Carabus each confined often to one mountain. 



The number of subspecies into which the Indo-Australian Papilios have 

 developed is very great,t and, when studying these insects, we were surprised to 

 find that, in opposition to the general view, not the males but the females appear 

 to be the fir.st affected by localised transmuting factors. In all cases, without 

 exception, where the distinguishing characters of a subspecies are found only in one 

 sex, it is ihe^ female and not the inale which exhibits them ; and further, in those 

 subspecies which are obviously different in all specimens of one sex, slightly or even 

 only occasionally diflerent in the other sex, it is again the/cw/fc that is the more 

 aberrant sex. If we further take into account the local aberrations as far as they 

 constantly and commonly appear among the normal specimens, we have thirty-six 

 cases among the ludo-Australian Pajjilios in which the localised variation is entirely 

 or almost entirely restricted to the female sex, while there is not a single subspecies 

 which is in the male much more ditfercnt from the allies than in t\\<i female. In 

 seasonal forms of Papilios tha females again exhibit a greater amount of diver- 

 gency than the males, a phenomenon which is strikingly illustrated by the Japanese 

 Papilio maeliaon hippocrates. The variability is in the females of the Indo- 

 Australiau Papilios altogether greater than in the males, or, to express it biologically, 

 the females are more easily affected by the causes of variation than the other sex. 

 If localised variation is the beginning of the divarication of a species into more 

 species, and we have seen that this is the only possible way by which divarication 

 can come about, those phenomena, which relate especially to pattern, admit no 

 other explanation than that, at least in all cases where the localised variation is 

 restricted, or nearly so, to the females, the transmutation of the species begins in 

 the. female sex, and that, therefore, the female is in advance of the male in respect 

 of the development into new species. Eimer and Fickert in their studies on the 

 Papilios come to the opposite result ; and that is, we think, due to tlieir nssnnii)tion 

 that the original pattern of the wings of Pajjilios consisted of " longitudinal " I'aiids 



• See this journal, IRil."). p. ISO. 



t See Rothschild, Nov. ZooL. 1895. p. 4G3. 



