306 A^iRIATION OF PLANTS AND ANIMALS. [Ch. XXXVL 



been ranked by ornithologists as true species, yet wliich pair 





freely and produce fertile ofPsprin 



All the different races of domestic dogs breed together, 



Hunter 



mule 



A 



ca- 



jackal and wolf must be classed as of the same species 

 because when crossed they produce fertile 

 pability of thus breeding together has often been proposed, 

 as the best practical test of a real distinctness of species. 

 The experiment with which we are most familiar relates to 

 the mixed offspring of the horse and the ass ; and in this 



■mule 



mule 



more 



luce. Such cases occur in Spain and Italy, 

 frequently in the West Indies and New 

 Holland ; but these mules have never bred in cold climates, 

 seldom in warm regions, and still more rarely in temperate 

 countries. But no instance is known of two such mules, 

 male and female, having bred together. 



The hybrid offspring of the she-ass and the stallion, the 

 rytvvo^ of Aristotle, and the hinnus of Pliny, differs from the 

 mule, or the offspring of the ass and mare. In both cases, 

 says Buffon, these animals retain more of the dam than of 

 the sire, not only in the magnitude, but in the figure of the 

 body ; whereas, in the form of the head, limbs, and tail, they 

 bear a greater resemblance to the sire. It seems rarely to 

 happen that any hybrids are truly intermediate in character 



between the two parents. 

 his experiments with the 



dog 



5 Hunter mentions that, m 

 and the wolf, one of the 



sembled the wolf much 



Wieormann 



Mena 



pointer and a she-wolf, two of the cubs resembled the common 



wolf-dog, but the third was like a pointer with hanging ears. 



The phenomena of hybridity in plants present a remarkame 



animal kincrdom 



more from 



iments 



numbers 



O -L •/ /» 



and taking small account of failures, provided that some o 

 the results of crossing are successful. 



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