ich 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 Mr. Blyth and Capt.
Hutton, that whole flocks of these crossed geese are kept in various
parts of the country; and as they are kept for profit, where neither
pure parent-species exists, they must certainly be highly fertile.

A doctrine which originated with Pallas, has been largely accepted
by modern naturalists; namely, that most of our domestic animals have
descended from two or more aboriginal species, since commingled by
intercrossing. On this view, the aboriginal species must either at first
have produced quite fertile hybrids, or the hybrids must have become in
subsequent generations quite fertile under domestication. This latter
alternative seems to me the most probable, and I am inclined to believe
in its truth, although it rests on no direct evidence. I believe, for
instance, that our dogs have descended from several wild stocks; yet,
with perhaps the exception of certain indigenous domestic dogs of South
America, all are quite fertile together; and analogy makes me greatly
doubt, whether the several aboriginal species would at first have freely
bred together and have produced quite fertile hybrids. So again there
is reason to believe that our European and the humped Indian cattle are
quite fertile together; but from facts communicated to me by Mr. Blyth,
I think they must be considered as distinct species. On this view of
the origin of many of our domestic animals, we must either give up the
belief of the almost universal sterility of distinct species of
animals when crossed; or we must look at sterility, not as an indelible
characteristic, but as one capable of being removed by domestication.

Finally, looking to all the ascertained facts on the intercrossing of
plants and animals, it may be concluded that some degree of sterility,
both in first crosses and in hybrids, is an extremely general result;
but that it cannot, under our present state of knowledge, be considered
as absolutely universal.