CONGENERS. 839 
deer was taken on board. On the question of the habitat of these 
animals, I have deemed it important to be very particular, and 
the result is that I cannot doubt that their nativities are as 
stated. 
Had both been found in the same range, I confess I should 
have long hesitated before concluding that the absence of the 
metatarsal gland in one, and its presence in the other, would 
alone justify us in declaring a specific difference; nor would it in 
any case, but from the fact that an examination of a great num- 
ber of individuals of most of the species, and a considerable num- 
ber of all, enable us to say that it is the most constant and uni- 
form of all the indicia to be found on any of them. Where it is 
wanting on one individual of a species, it is wanting on all, and 
where it is present on one, it is present on all, and is precisely 
alike on all of the same species, and entirely unlike that found on 
either of the other species; so that no two of different species at 
all resemble each other in this regard, while in no two of the same 
species can any difference be detected. If other naturalists have 
attached less importance, or even no importance, to this than I 
do, I must be pardoned for saying that I think it is because they 
have studied it less. 
Had I found this gland present or absent in both, and so been 
unable to point out any substantial difference between them 
although coming from so widely separated Jocalities, what should 
I say then as to their specific identity ; when it is certain that 
the races must have been separated for an immense period of 
time, to say the least? He who will answer the following ques- 
tion will answer that. When races or animals are alike, but in 
nowise related to each other, are they of the same species? In 
connection with this subject, I repeat, that under the most fav- 
orable circumstances I found these deer to interbreed very reluc- 
tantly, and months after the proper season, but then the union 
was fully fertile, for the doe produced twins; however, these 
were still-born, or died very soon after birth. Not the least indi- 
cation of the metatarsal gland can be found on either of these 
fawns, which, of course, are added to my collection. I do not 
know but hybrids are as liable to be twins as others. Mares 
very rarely have twins, and yet I have heard of one well au- 
thenticated instance of twin mules in my own neighborhood. 
Altogether I think it very clear that there is a sexual aversion 
observed in these deer which is usually observed between individ- 
uals of different species, which augments the evidence of specific 
