178 



THE GENESIS OF SPECIES. 



[CHAP. 



likewise "homologous parts, yet of another kind ; that is 

 they are the same parts existing in animals of different 

 species. 



In contrast to this, the wing of the humming-bird and 

 the wing of the humming-bird moth are not homologous at 

 all, or in any sense; for the resemblance between them 

 consists solely in the use to which they are put, and is 



SKELETON OF THE FLYING DRAGON. 



(Showing the elongated ribs which support the flitting organ.) 



therefore only a relation of analogy. There is no relation 

 of homology between them, because they have no common 

 resemblance as to their relations to surrounding parts, or 

 as to their mode of origin. Similarly, there is no homology 

 between the wing of the bat and that of the flying-dragon, 

 for the latter is formed of certain ribs, and not of limb 

 bones. 



