20 GERMINAL SELECTION. 



are the same on both the upper and the lower surfaces 

 of the wings. Possibly the expression of a law might 

 be seen in this fact, and it might be said, the coloration 

 of the Heliconids runs through from the upper to 

 the under surface. But among numerous imitators 

 of the Heliconids is the genus Protogonius, which 

 has the coloration of the Heliconids on its upper sur- 

 face, but on its lower exhibits a magnificent leaf- 

 design. During flight it appears to be a Heliconid and 

 at rest a leaf. How is it possible that two such totally 

 different types of coloration should be combined in 

 a single species, if any sort of inner rigorous necessity 

 existed, regulating the coloration of the two wing- 

 surfaces? Now, although we are unable to prove 

 that the Protogonius species would have perished 

 unless they possessed this duplex coloration, yet it 

 would be nothing less than intellectual blindness to 

 deny that the butterflies in question are effectively 

 protected, both at rest and during flight, that their 

 colorations are adaptive. We do not know their prim- 

 itive history, but we shall hardly go astray if we 

 assume that the ancestors of the Protogonius species 

 were forest-butterflies and already possessed an under 

 surface resembling a leaf. By this device they were 

 protected when at rest. Afterwards, when this pro- 

 tection was no longer sufficient, they acquired on their 

 upper surface the coloration of the exempt species 

 with which they most harmonised in abode, habits of 

 life, and outward appearance. 



At the same time it is explained why these butter- 

 flies did not acquire the coloration of the Heliconids 

 on the under surface. The reason is, that in the atti- 

 tude of repose they were already protected, and that 

 in an admirable manner. 



