HAYBRIDITY OF THE CERVIDE. 311 
take place it is more apt to be fertile, than when the individuals 
are in confinement or semi-domestication. Indeed we should an- 
ticipate such a result, for as I show elsewhere, nearly all wild 
animals are less fertile in confinement than in the wild state, and 
this arises not so much because of less inclination to sexual inter- 
course, but because such intercourse when it does occur is less 
fruitful. 
But it is not my purpose to go far back of the present and 
grope my way in intricate paths which at best must be but im- 
perfectly lighted up, and discuss subjects not embraced in my 
present inquiry, and which I am less qualified to examine than 
others who can bring to their elucidation a much broader inquiry 
and much more abundant facts than are at my command. My 
ambition rather is to bring new facts arising within the limited 
sphere of my observations, which will serve as a single brick to 
be placed by other and more competent hands in the great struc- 
ture of ultimate truth, the construction of which is already com- 
menced in the world of science. He who shall furnish the most 
accurately observed facts, will provide the most acceptable mate- 
rial for the hands of the architect, and an exhaustive inquiry as to 
facts even within a very narrow sphere will have only done that 
which must be done in reference to all other subjects before the 
skillful generalizer will be provided with the necessary material 
for his great work. 
A very common error has prevailed, even to some extent in 
scientific quarters, that hybrids, or the issue of parents of different 
species, are necessarily unfertile; in other words, if a supposed 
hybrid is capable of propagation it is conclusive evidence that the 
parents were of the same species. 
The fact that hybrids are less likely to be productive or are 
less fertile than the progeny of parents of the same species is 
undoubtedly true, and a fertile offspring goes a very long way to 
prove that the parents were of the same species; but there are 
many well anthenticated cases of fertile hybrids. 
The most common and familiar hybrid is the cross between the 
ass and the mare, which as a general rule is incapable of propaga- 
tion, either among themselves or with either parent, and this no 
doubt has had a large influence in creating the general belief re- 
ferred to; still there are many cases where the mule has bred 
from the horse; and Dr. Morton says that this is very common 
in Spain. In his essay on hybridity, published in the “ American 
Journal of Arts and Sciences,” 1847, page 212, Dr. Morton has 
