CONGENERS. 337 
while in all other respects they exactly correspond, and no ra- 
tional doubt should exist of their specific identity. The mule 
deer in the Rocky Mountains is four times as large as in Lower 
California, which difference is also supplemented by the fact that 
the change in the antler is quite as great, for on all of the small 
variety the antler has ceased to be bifurcated, but presents a 
spike like that of the yearling deer of the north; or if ever bi- 
furcated that feature is as rare as on the first antlers of the bet- 
ter developed variety of the north, and yet I do not hesitate to 
rank them in the same species from their exact similitude in all 
other respects, according to the reliable information I have re- 
ceived of them. With the same propriety might we deny that 
the Fuegian and the Patagonian are of the same species. 
In considering this question of specific identity we should by 
no means forget that these animals freely interbreed whenever 
they have opportunity, and their progeny proves as fertile as 
either of the parents, as has been shown in the article on Hy- 
bridity. While this should not be considered as conclusive evi- 
dence of specific identity, it is important cumulative evidence in 
that direction. If in the wild state in the forest it were found 
that the sexes showed the same inclination for each other which 
they show for the opposite sex of their own varieties, this would 
add vastly to the weight of the evidence and would: make out a 
very strong primé facie case at least ; for, as is shown in another 
place, the sexes of separate species have a natural sexual aversion 
for each other which is more marked in the female, and although 
this no doubt may be sometimes overcome in the wild state and 
without constraint, and so hybrids produced voluntarily, probably 
if the truth could be known we should find that the female re- 
ceived the embraces of the male only when she could not find a 
male of her own species. After years of experimenting with as 
great facilities as are likely to be often enjoyed, I at least have 
been unable to obtain a hybrid under other conditions, and even 
when no proper male has been on any part of the grounds suc- 
cess has very rarely attended my efforts, as is more fully shown 
in another place. 
After the best investigation and consideration I have been 
able to give the subject -—and my opportunities have not been 
stinted, —I am inclined to fall back into the ranks of those nat- 
uralists who first compared the two animals, who failed to find 
sufficient differences to justify the erection of a new species to 
accommodate the new variety found on this continent, and I 
22 
