78 



THE GENESIS OF SPECIES. 



[Chap. 



tiles — we meet witli an approximation to the structure of 

 the but, but in the pterodactyl we have only one finger 

 elongated in each hand : a striking examj)le of how the 

 very same function may be provided for by a modilicalion 

 similar in principle, yet surely manifesting the indepen- 

 dence of its origin. When we go to lower animals, we lind 

 llight produced by organs, as the wings of insects, which 

 are not even modilied limbs at all; or we find even the 



SKELETON OF THE FLYING-DBAOON. 



(Sho\\iDg the elongated ribs which support the flitting organ.) ^ 



function sometimes subserved by quite artificial means, as 

 in the alirial spiders, which use their own threads to float 

 with in the air. In the vegetable kingdom the atniosphere 

 is often made use of for the scattering of seeds, by their 

 l)cing furnished with special structures of very different 

 kinds. The diverse modes by which such seeds are dis- 

 persed are well expressed by Mr. Darwin. He says : ^ 



••' " Origin of Species," 6th edit., p. 235. 



