172 THE LESSON OF EVOLUTION 



appear to have no use but show no degeneration. 

 Of such are the pincers of ear- wigs, of which Dr. 

 Sharp, whose knowledge of insects is unrivalled, 

 says : ' ' They are occasionally used by the insects 

 as a means of completing the process of packing up 

 the wings ; but in many species it is not probable 

 that they can be used for such purpose, because their 

 great size and peculiarly distorted forms render them 

 unsuitable for assisting in a delicate process of 

 arrangement; they are, too, always present in the 

 wingless form of the family."* 8 Still we must 

 presume that these pincers, have some use, although 

 we do not know what it is ; for they are so well 

 developed and never rudimentary. It is the same 

 with the remarkable modifications in the antennae 

 of beetles and flies. We cannot help thinking that 

 all the different forms have different uses, although 

 we cannot detect them. 



But the case is different with the insignificant 

 characters which I have already mentioned, such as 

 the folding of the enamel in the teeth of elephants. 

 And we are confirmed in this opinion because no 

 advantage has been gained by different foldings. 

 Take now the case of the hairs on the eyes of some 

 Diptera. Of the two common blue-bottle flies in 

 New Zealand, one has the eyes hairy and the other 

 has them naked. Both species frequent the same 

 localities, both appear to have the same habits, and 

 both are equally common. Now by the principle 

 of natural selection these hairy eyes cannot be 

 useful, or the species that has them would prepon- 



* s Cambridge Xat. Hist. Insects, Part I., p. 208. 



