CHAPTER XII 

 THE CROSS-BREEDING OF RACES 



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WE have seen that there is no simple rule as to 

 the "mating" of individuals of a species with 

 individuals of another closely allied but distinct 

 species. Such mating very rarely comes about in natural 

 conditions, but man by his interference sometimes succeeds 

 in procuring " hybrids " between allied species. Hybrids 

 between species belonging to groups so different as to be 

 distinguished by zoologists as distinct "families" or 

 "orders" are quite unknown under any circumstances. 

 Such remoteness of natural character and structure as is 

 indicated by the two great divisions of hoofed mammals 

 — the even-toed (including sheep, cattle, deer, antelopes, 

 giraffes, pigs and camels), and the odd-toed (including 

 tapirs, rhinoceroses, horses, asses and zebras) is an 

 absolute bar to inter-breeding. So, too, the carnivora 

 (cats, dogs, bears and seals, and smaller kinds) are so 

 remote in their nature from the rabbits, hares and rats — 

 called " the rodents " — that no mating between members 

 of the one and the other of these groups has ever been 

 observed, either in nature or under artificial conditions. 



Even when individuals of closely allied species mate 

 with one another it is a very rare occurrence that the 

 hybrids so produced ripen their ova and sperms so as 

 to be capable of carrying on the hybrid race, though 

 sometimes they do ripen them and breed. The great 

 naturalist Alfred Wallace, in his most valuable and 



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