140 BLASTOGENIC VARIATIONS, 



false with the greyhounds, and all but one of the litter 

 were destroyed. Two years later, this young dog was 

 seen by a friend of the owner, and he declared him to 

 be the image of his old pointer bitch, the only blue and 

 white pointer of pure descent he had ever seen. On 

 close enquiry, it was proved that the dog was the great- 

 great- grandson of the bitch, and so, on Galton's law, it 

 should have received only fg- part of its heritage from 

 her. Another even more remarkable instance is that 

 of a calf which was coloured in a very peculiar manner, 

 its legs, belly, and part of the tail being white, and the 

 remainder black. Its great-great-great-great-grand- 

 father was coloured in the same peculiar manner, but 

 all the intermediate offspring were black. Hence the 

 calf reverted in its colour markings to an ancestor from 

 which it should have drawn only ^^ part of its 

 heritage. 



It is when two distinct races are crossed that the 

 tendency in the offspring to reversion most often de- 

 clares itself. No examples are more striking than 

 those obtained by Darwin in the case of the domestic 

 pigeon. For instance,* he paired a mongrel female 

 Barb-fantail with a mongrel male Barb-spot, neither of 

 these mongrels having the least blue about them. 

 " Nevertheless the offspring from these two mongrels 

 was of exactly the same blue tint as that of the wild 

 rock-pigeon from the Shetland Islands over the whole 

 back and wings; the double black wing bars were 

 equally conspicuous; the tail was exactly alike in all its 

 characters, and the croup was pure white; the head, 

 however, was tinted with a shade of red, evidently de- 

 *L. c. t i. p. 209. 



