between Man and all oilier Animals. 8 1 



so far as can yet be shown, at least in animals, where fecun- 

 dation cannot happen fortuitously, in every instance referable 

 to human interference. As yet, I have failed to meet with a 

 single satisfactory instance, wherein commixture of species 

 could not be directly traced to man's agency, in superimposing 

 a change on the constitution of the female parent. This is a 

 subject of exceeding interest ; and I am glad to avail myself 

 of every occasion to endeavour to incite some to undertake 

 its further investigation. There can be little doubt that cer- 

 tain of our domestic races, as the common fowl, are derived 

 from a plurality of species, which, however, do not blend in 

 wild nature ; so that their union (assuming the hypothesis to 

 be correct) may here, at least, be fairly ascribed to domestica- 

 tion. Still, when we consider that separate species (i. e. races 

 not. descended from a common stock) exhibit, as is well 

 known, every grade of approximation, from obviously distinct 

 to doubtfully identical, there appears, I think, sufficient rea- 

 son at least to suspect that circumstances may sometimes 

 combine to induce those nearest allied to commingle. That 

 the mixed progeny, too, would in some instances be mutually 

 fertile, I know in the case of the hybrid offspring of the 

 A'nser cygnoides, and the common goose ; but, in birds gene- 

 rally, the converse nevertheless obtains, as is particularly 

 instanced, I have learned, by the hybrid Fringillidse reared 

 in confinement ; and also the mule betwixt the common fowl 

 and pheasant; the males of all which appear (from a variety 

 of instances I have been fortunate in collecting) to have been 

 incompetent to fecundate the eggs produced.* Perhaps the 

 superior size, too, of these hybrids generally to that of either 

 of their parent species may be explicable on the principle 

 which occasions the large growth of capons. However, none 

 of the species here alluded to are by any means so closely 

 allied as many that are known to exist ; and, therefore, as in 

 the vegetable world the degree of fertility in hybrids is in the 

 ratio of that of affinity between the parents, those derived 

 from very approximate species being, apparently, quite as pro- 

 lific as the pure race, analogy would lead us to infer that the 

 same law holds in the animal creation. At present, we have 

 no proof of it: and I may conclude the subject by observing 

 that the cases of supposed union (apart from human influ- 

 ence) betwixt the carrion and hooded crows, so often insisted 

 on, are inconclusive, inasmuch as it does not appear that the 

 individuals were ever examined and compared, although black 

 varieties of Corvus Cornix have been several times known to 

 occur. Indeed, I have myself examined a female specimen, 



* Since writing this, I have been informed of a solitary instance of a 

 male goldfinch mule producing offspring with a hen canary. 



