24 GERMINAL SELECTION. 



hind wing and the other to the fore wing, and that 

 the two fit each other exactly when the butterfly is in 

 the attitude of repose, but not otherwise. Now these 

 two pieces of the leaf-rib do not begin on correspond- 

 ing spots of the two wings, but on absolutely non- 

 identical spots. And the same is also true of the 

 lines which represent the lateral ribs of the leaf. 

 These lines proceed in acute angles from the rib ; to the 

 right and to the left in the same angle, those of the 

 same side parallel with each other. Here, too, no 

 relation is noticeable between the parts of the wings 

 over which the lines pass. The venation of the wing 

 is utterly ignored by the leaf-markings, and its sur- 

 face is treated as a tabula rasa upon which anything 

 conceivable can be drawn. In other words, we are 

 presented here with a bilaterally symmetrical figure 

 engraved on a surface which is essentially radially 

 symmetrical in its divisions. 



I lay unusual stress upon this point because it shows 

 that we are dealing here with one of those cases which 

 cannot be explained by mechanical, that is, by natural 

 means, unless natural selection actually exists and is 

 actually competent to create new properties ; for the 

 Lamarckian principle is excluded here ab initio, see- 

 ing that we are dealing with a formation which is 

 only passive in its effects ; the leaf-markings are ef- 

 fectual simply by their existence and not by any func- 

 tion which they perform; they are present in flight 

 as well as at rest, during the absence of danger, as well 

 as during the approach of an enemy. 



Nor are we helped here by the assumption of purely 

 internal motive forces, which Nageli, Askenasy, and 

 others have put forward as supplying a mechanical 

 force of evolution. It is impossible to regard the co- 



