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distinct from its two parents, first by its external colour, and 
secondly by the vomerine dentition. 
Another cross, which so far seems destined to continue, if it 
be placed in suitable ponds, is that between the American and 
British chars, termed struans at Howietoun. 
We find similar instances among pheasants which have been 
introduced into and will thrive in this country, for different 
species cross, yet without inducing sterility. But I would more 
especially allude to the bovine experiment at the Zoological 
Gardens, where we find a zebu, Bos indicus, interbreeding with 
a gayal, Bibos frontalis, and the hybrids again crossed with a 
bison, Bison Americanus, but in all of which crossing the bull 
was of an unmixed breed. Here are what are commonly con- 
sidered three distinct genera hybridizing, and so far as I know, 
the last offspring may be fertile. This would seem to show 
that new forms, or some alterations in old forms, may be 
produced by hybridization; but only so far, as has been already 
shown, among parents that are naturalized, and would continue 
their race. 
Blyth remarked that “the results of experiments instituted 
on sheep by the Agricultural Society of Séverac fully warrant 
the conclusion that where species exist under circumstances 
favourable for their increase, a greater number of that sex is 
produced, which, in polygamous animals, is most effectual for 
their multiplication: whereas the contrary obtains, probably, in 
proportion to the difficulty of obtaining a livelihood.” (Charles- 
worth, Magazine of Natural History, 1837, i., p.84.) This would 
appear to point out that abundance of food is one means of 
increasing the number of certain species by causing the offspring 
to be of the most prolific sex. This would seem to be confirmed 
by the well-fed bovine experiment at the Regent’s Park 
Zoological Gardens, which I have just cited, as the young were 
invariably females; whereas at Halle the produced hybrids were 
nine males and ten females; but we know nothing of the con- 
ditions under which they were reared: still the bulls were 
invariably sterile, showing some morphological or physiological 
changed condition in the generative organs. 
