18 DOMESTIC PIGEONS. [CHAP. I 



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 produced 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 improbable 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 : I 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 succeeding 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. These two distinct cases of 

 reversion are often confounded together 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 observa- 

 tions, 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 probably 

 quite correct, if applied to species closely related to each other. 

 But to extend it so far as to suppose that species, aboriginally 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 

 having formerly made seven or eight supposed species of pigeons 

 to breed freely under domestication ; these supposed species being 

 quite unknown in a wild state, and their not having become 

 anywhere feral ; these species presenting certain very abnormal 



