ON SPECIES, HYBRIDS, AND VARIETIES. 165 



it is, perhaps, possible, that the physical constitution of the hybrids between 

 them, may be so ordered as to enable them to reproduce offspring by their 

 mutual union ; and, moreover, that the fertility of hybrids inter se, may be 

 much influenced by the natural fertility of their parents, that is, that where 

 two species, each, naturally, very fertile, produce hybrids, these hybrids 

 may partake of the prolific nature of both parents, to such an extent as to 

 be fertile inter se. However it may be accounted for, it cannot be doubted 

 that, in some few cases, the hybrids between really distinct species are fertile, 

 notwithstanding the weight of authority to the contrary.* According to 

 Buffon, the offspring of the male Goat and Ewe are prolific ; and if the ideas 

 of Mr. Eyton be correct, respecting the specific distinction between the 

 Chinese Hog and the common European Swine, the offspring of which are 

 fertile inter se, there is an interesting case in point. (See Proceedings 

 Zool. Soc. 1837, p. 23.) 



It is commonly supposed, that the fertility of so-called hybrids, inter se, 

 is sufficient to prove the specific identity, or common primitive origin, of the 

 parents. The consequence is by no means clear. A permanent difference 

 of form, however trivial, distinct habits and instincts, transmitted from age 

 to age, however minute the distinction may be, are sufficient, it is con- 

 tended, to establish the originality and genuineness of species. How close is 

 the Grey-lag Goose (Anser palustris) to the Bean Goose (Anser ferus) ; 

 how near the Wild Swan (Cygnus ferus), to Bewick's Swan (Cygnus 

 Bewickii) ; and how much closer still is the latter to the Cygnus buccinator 

 of North America ; yet, on these instances (and we might fill pages with 

 others even more pertinent), the species are regarded as genuine, because, 

 however superficial or slight the differences may be between them, these 

 differences are constant ; nor would the fertility of hybrids between them 

 invalidate the conclusion. Besides, it would appear that, although the first 

 generation of hybrids may be fertile inter se, either their progeny, after 

 the first or second remove, cease to be so (the prolific power becom- 

 ing feebler), or that the progeny return back to the most influential of the 

 parent stocks, and completely merge into it ; so that the ad libitum conti- 

 nuance of a factitious race would seem to be denied by Nature. With this 

 allowance, then, must the non-prolific nature of hybrids, as a test of the 

 genuineness of species, be taken, rather than in an absolute, or unqualified, 

 sense. Nay, the very circumstance of hybrids returning (where they do not 



Pallas entertained the opinion that our Sheep, Dogs, and, perhaps, Poultry, are factitious beings, 

 not descended from any single wild original stock, but from a mixture of nearly allied primitive species, 

 whose hybrid offsprings have possessed prolific powers. He observes, that those domesticated animals 

 which either do not intermix with other species, or which produce with others an unprolific progeny, 

 are very little changed, however completely and anciently they may have been under the dominion of 

 Man : such, he regards to be the Horse, the Ass, the Ox, the Hog, the Camel, the Dromedary, and the 

 Rein Deer. The varieties of the Dog have ever been a stumbling-block in the way of naturalists ; but 

 we cannot regard the Sheep, or the domestic Fowl, as hybrids. The ideas of Pallas, however, are well 

 worth consideration. 



