Chap. i. Domestic Pigeons. 10 



<v 



tail and red spot on the forehead, and which notoriously breeds very 

 true ; the mongrels were dusky and mottled. I then crossed one of 

 the mongrel barb-fantails with a mongrel barb-spot, and they pro- 

 duced a bird of as beautiful a blue colour, with the white loins, 

 double black wing-bar, and barred and white-edged tail-feathers, as 

 any wild rock-pigeon! We can understand these facts, on the 

 well-known principle of reversion to ancestral characters, if all 

 the domestic breeds are descended from the rock-pigeon. But if 

 we deny this, we must make one of the two following highly im- 

 probable suppositions. Either, first, that all the several imagined 

 aboriginal stocks were coloured and marked like the rock-pigeon, 

 although no other existing species is thus coloured and marked, so 

 that in each separate breed there might be a tendency to revert to 

 the very same colours and markings. Or, secondly, that each 

 breed, even the purest, has within a dozen, or at most within a 

 score, of generations, been crossed by the rock-pigeon : 1 say within 

 a dozen or twenty generations, for no instance is known of crossed 

 descendants reverting to an ancestor of foreign blood, removed by a 

 greater number of generations. In a breed which has been crossed 

 only once, the tendency to revert to any character derived from 

 such a cross will naturally become less and less, as in each, succeed- 

 ing generation there will be less of the foreign blood ; but when 

 there has been no cross, and there is a tendency in the breed to 

 revert to a character which was lost during some former generation, 

 this tendency, for all that we can see to the contrary, may be 

 transmitted undiminished for an indefinite number of generations 

 Ihese two distinct cases of reversion are often confounded toother 

 by those who have written on inheritance. 



Lastly, the hybrids or mongrels from between all the breeds of 

 the pigeon are perfectly fertile, as I can state from my own obser- 

 vations, purposely made, on the most distinct breeds. Now, hardly 

 any cases have been ascertained with certainty of hybrids from two 

 quite distinct species of animals being perfectly fertile. Some 

 authors believe that long-continued domestication eliminates this 

 strong tendency to sterility in species. From the history of the 

 dog, and of some other domestic animals, this conclusion is pro- 

 bably quite correct, if applied to species closely related to each 

 other. But to extend it so far as to suppose that species, aborigi- 

 nally as distinct as carriers, tumblers, pouters, and fantails now are 

 should yield offspring perfectly fertile inter se, would be rash in the 

 extreme. 



From these several reasons, namely,— the improbability of man 

 navmg formerly made seven or eight supposed species of pigeons to 



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