Chap. XIV. RECAPITULATION. 473 



elusion when we look, for instance, at the logger-headed 

 duck, winch has wings incapable of flight, in nearly 

 the same condition as in the domestic duck ; or when 

 we look at the burrowing tucutucu, which is occasionally 

 blind, and then at certain moles, which are habitually 

 blind and have their eyes covered with skin ; or when 

 we look at the blind animals inhabiting the dark caves 

 of America and Europe. In both varieties and species 

 correlation of growth seems to have played a most im- 

 portant part, so that when one part has been modified 

 other parts are necessarily modified. In both varieties 

 and species reversions to long-lost characters occur. 

 How inexplicable on the theory of creation is the occa- 

 sional appearance of stripes on the shoulder and legs 

 of the several species of the horse-genus and in their 

 hybrids! How simply is this fact explained if we 

 believe that these species have descended from a striped 

 progenitor, in the same manner as the several domestic 

 breeds of pigeon have descended from the blue and 

 barred rock-pigeon ! 



On the ordinary view of each species having been 

 independently created, why should the specific charac- 

 ters, or those by which the species of the same genus 

 differ from each other, be more variable than the generic 

 characters in which they all agree ? Why, for instance, 

 should the colour of a flower be more likely to vary in 

 any one species of a genus, if the other species, supposed 

 to have been created independently, have differently co- 

 loured flowers, than if all the species of the genus have the 

 same coloured flowers ? If species are only well-marked 

 varieties, of which the characters have become in a high 

 degree permanent, we can understand this fact; for 

 they have already varied since they branched off from a 

 common progenitor in certain characters, by which they 

 have come to be specifically distinct from each other ; 



