254 
HYBRIDISM. 
Chap. VIII. 
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 wild species, since commingled by inter¬ 
crossing. On this view, the aboriginal species must 
either at first have produced quite fertile hybrids, or 
the hybrids must have become in subsequent genera¬ 
tions 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 per¬ 
haps 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 to¬ 
gether 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 uni¬ 
versal sterility of distinct species of animals when 
crossed; or we must look at sterility, not as an in¬ 
delible characteristic, but as one capable of being re¬ 
moved by domestication. 
Finally, looking to all the ascertained facts on the 
intercrossing of plants and animals, it may be con¬ 
cluded that some degree of sterility, both in first crosses 
