The Making of Species 
types, such as happens when colour-forms are 
crossed, 
M. Suchetet bred hybrid gold = Amherst 
pheasants for four generations, and they retained 
the hybrid character. The young bred by 
Darwin from a pair of common = Chinese geese 
hybrids “resembled,” he says, “in every detail 
their hybrid parents.” 
When hybrids have been—as has far more 
usually been the case — bred back to one 
of the pure stocks, the hybrid characters have 
shown, as might be expected, a tendency quickly 
to disappear. The three-quarter-bred polar bear 
now in the London Zoological Gardens is a 
pure polar save for a brown tinge on the back. 
A three-quarter Amherst = gold pheasant in the 
British Museum is a pure Amherst save for the 
larger crest, and a patch of red on the abdomen. 
When three-quarter-bred pintail = common duck 
hybrids were bred back to the pintail, the off- 
spring “lost all resemblance to the common 
duck.” In the case of the Argali-urial herd of 
wild sheep above-mentioned, after the usurping 
Argali ram had been killed by wolves, the hybrids 
bred with the urials, with the result that the herd 
renewed the appearance of pure urial. 
Thus, except in the very improbable case of a 
family of hybrids going off and starting a colony 
by themselves, the effect of hybridism on the 
evolution of species seems likely to have been 
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