SPECIES AND VARIETY. 231 



wild animals. We must therefore admit, for all the species 

 which we know at present, as sufficiently distinct and con- 

 stant, a distinct origin and common date. On the other 

 hand, the fruitful intermixture which art has accomplished, 

 of some of these species, will not justify us in ascribing to 

 them identity of race or origin, when we see them in the 

 natural wild state distinguished by constant characters from 

 the type of the neighbouring species, and always producing 

 an offspring marked by these characters. 



Since neither the principle of breeding, nor the constancy 

 of particular characters, are sufficient in all cases to enable 

 us to judge of species — and since these fail, particularly in 

 the domestic kinds, where their aid is principally required — 

 we must resort at last to the criterion recommended by 

 Blumenbach, and draw our notions of species in zoology 

 from analogy and probability. If we see two races of animals 

 resembling each other in general, and diffi^ring only in cer- 

 tain respects, according with what we have observed in other 

 instances, we refer them without hesitation to the same 

 species, although the diffijrence should be so considerable as 

 to affisct the whole external appearance. On the contrary, if 

 the difference should be of a kind whicli has never arisen, 

 within our experience of the animal kingdom, as a variety, 

 we must pronounce them to belong to distinct species, even 

 although there should be, on the whole, a great general 

 resemblance between the two. " I see,'' says this acute and 

 judicious naturalist, " a remarkable difference between the 

 Asiatic and African elephants, in the structure of the molar 

 teeth. Whether these inhabitants of such distant regions 

 will ever be brought to copulate together, and whether this 

 formation be universal, is uncertain ; but it exists in all 

 the specimens I have seen or heard of; and I know no ex- 

 ample of molar teeth changed in such a manner by degene- 

 ration, or the action of adventitious causes : therefore I con- 

 jecture, from analogy, that these elephants are not mere 

 varieties, but truly different species. On the other hand, I 

 hold the ferret (mustela furo) to be only a variety of tlie pole- 

 cat (m. putorius), not so much because they produce toge- 



