358 THE EVOLUTION THEORY 



is continuofl on to the tip of the anterior win^-. This may be seen, 

 for instiince. in tlu- oeinis Amva, which is ricli in species. But even 

 then a still further increase of the resemblance is possible, for, as is 

 well known, there are not infrequently imitations of the lateral veins 

 of thr leaf as well, or dark spots which faithfully reproduce the 

 mould-spot on a damp, decaying leaf, or colourless transparent spots 

 which probably siuudate dewdrops, and so on. All these are variations 

 relatin^x to individual and distinct o-roups of wing-scales, which 

 liave varied transmissibly and independently, that is, each of them 

 has been produced by a variation in the germ-plasm, which brought 

 about a change in this particular area of the body and in no other. 



Let us for a moment assume the impossible, and suppose that we 

 could look on at the evolution of such a leaf-buttei-fly ; the beginning 

 of the leaf-imitation might have its cause in the fact that an ancestral 

 form of Kidlima, which had previously lived in the meadows, exhibited 

 on the part of some of its descendants a migration to the woods, and 

 thus divided into two groups, with a different manner of life — a 

 meadow form and a wood form. The latter adapted itself to sitting 

 among leaves, and the midrib of a leaf developed on its wings. In 

 a germ-plasm without ' primary constituents ' this variation could 

 only depend on a uniform variation of all the parts, for these parts 

 are either alike among themselves, or at any rate have the same value 

 for every part of the finished organism. But the germ-plasm of the 

 new breed must somehow differ from that of the ancestral form, 

 otherwise it could produce no new variety, but only the ancestral 

 form over again. But how could an animal differing only in one 

 minute part arise from a germ-plasm which has varied in all its parts, 

 and how could such little steps of variation be repeated many times 

 in the course of the phylogeny without the corresponding variations 

 of the germ-plasm becoming so intense that not only the wing- 

 markings but everything about the animal would be altered likewise ? 

 And yet these 'leaf-pictures' have not originated suddenly, but 1)}^ 

 many small steps, so that the germ-plasm must have varied in toto 

 a hundred times in succession if there are no primary constituents. 



In the Indian species, Kallwia 'paralecta, there are no fewer 

 than five well-marked varieties, the differences between which depend 

 solely on the manner in which the leaf-picture on the wing is 

 elaborated, /o?' the upper surface of the wing is alike in all. Even 

 a cursory observation of a collection of these butterflies shows 

 that the lateral veins of the leaf -picture are quite different in number, 

 distinctness, and length in the different individuals. On the right 

 half of the wing there may be as many as six of them indicated 



