86 



THE EVOLUTION THEORY 



down so artistically that the ' upward turning leaf-stalk is in juxta- 

 p(\sition to a twig,' we may answer that a bird iiying fast is not 

 likely to look to see whether every leaf in the profusion of foliage 

 in the primitive forests is properly fastened to its stalk or not, any 

 more than we should do in the ease of a painted bush, on which many 

 a leaf lias the appearance of floating in the air, just as in nature, or in 

 its faithful copy, the photograph. 



Quite diflerent from the leaf-marking either of CoeiiopJdehia 

 or Kallnna is that of one of the Satyrides of the lower Amazon 

 \alley, Gcvrois chorinceus (Fig. 15). If one spreads this butterfly 



out in the usual 

 V way it does not 



'■^^ look in the least 



like a leaf, and one 

 only sees a number 

 of curiously placed 

 disconnected stripes 

 on the under sur- 

 face of the wino;. 

 But if the wings 

 be folded too-ether 

 to correspond with 

 the sitting position 

 of the butterfly, 

 there appears the 

 figure of a leaf, 

 of which, however, 

 only half is present, 

 and whose midrib 

 (mr) runs obliquely 

 forward from the 

 inner angle of the 

 posterior wing. Here, again, it is not difficult to guess that this 

 straight stripe has arisen, by displacement and straightening, from 

 a curved line inherited from some remote ancestor, and it is these 

 precise changes which are the work of the adaptive processes of 

 natural selection. The same applies to the lateral ribs (sr), which are 

 here four in number. 



But even the division of the wing surface by a single dark line, 

 such as that which crosses the middle of the posterior wing of 

 Hebomoja (Fig. 9), an Indian butterfly, heightens not inconsiderably 

 the resemblance of the resting buttei% to a leaf, a resemblance which 



Fig. 15. ^ Ccerois chorinceus, from the lower Amazon, in its 



resting attitude. V, anterior wing. H, jDOsterior wing. 



midrib of the apparent leaf, sr, lateral veins, 

 a leaf-stalk. 



mr. 



st, hint of 



