Chap. VIIL 
STEEILITY. 
253 
should be perfectly fertile. Again^ with respect to the 
fertility in successive generations of the more fertile 
hybrid animals, I hardly know of an instance in which 
two families of the same hybrid have been raised at the 
same time from different parents, so as to avoid the 
ill effects of close interbreeding. On the contrary, 
brothers and sisters have usually been crossed in each 
successive generation, in ‘ opposition to the constantly 
repeated admonition of every breeder. And in this case, 
it is not at all surprising that the inherent sterility in 
the hybrids should have gone on increasing. If we 
were to act thus, and pair brothers and sisters in the 
case of any pure animal, which from any cause had the 
least tendency to sterility, the breed would^assuredly be 
lost in a very few generations. 
Although I do not know of any thoroughly well-authen¬ 
ticated cases of perfectly fertile hybrid animals, I have 
some reason to believe that the hybrids from Cervulus 
vaginalis and Eeevesii, and from Phasianus colchicus 
with P, torquatus and with P. versicolor are perfectly 
fertile. There is no doubt that these three pheasants, 
namely, the common, the true ring-necked, and the 
Japan, intercross, and are becoming blended together 
in the woods of several parts of England. The hybrids 
from the common and Chinese geese (A. cygnoides), 
species which are so different that they are generally 
ranked in distinct genera, have often bred in this 
country with either pure parent, and in one single 
instance they have bred inter se. This was effected 
by Mr. Eyton, who raised two hybrids from the same 
parents but from different hatches; and from these two 
birds he raised no less than eight hybrids (grandchildren 
of the pure geese) from one nest. In India, however, 
these cross-bred geese must be far more fertile; for 
I am assured by two eminently capable judges, namely 
