t 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 Captain 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 or perfectly
fertile.

With our domesticated animals, the various races when crossed together
are quite fertile; yet in many cases they are descended from two or more
wild species. From this fact we must conclude either that the aboriginal
parent-species at first produced perfectly fertile hybrids, or that the
hybrids subsequently reared under domestication became quite fertile.
This latter alternative, which was first propounded by Pallas, seems by
far the most probable, and can, indeed, hardly be doubted. It is, for
instance, almost certain that our dogs are descended from several wild
stocks; yet, with perhaps the exception of certain indigenous domestic
dogs of South America, all are quite fertile together; but 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 I have lately acquired decisive evidence that the crossed
offspring from the Indian humped and common cattle are inter se
perfectly fertile; and from the observations by Rutimeyer on their
important osteological differences, as well as from those by Mr. Blyth
on their differences in habits, voice, constitution, etc., these two
forms must be regarded as good and distinct species. The same remarks
may be extended to the two chief races of the pig. We must, therefore,
either give up the belief of the universal sterility of species when
crossed; or we must look at this sterility in animals, not as an
indelible characteristic, but as one capable of being removed by
domestication.

Finally, considering 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.

LAWS GOVERNING THE STERILITY OF FIRST CROSSES AND OF HYBRIDS.

We will now consider a little more in detail the