180 NEW YORK ZOOLOGICAL SOCIETY. 
varying abundance, to the Gulf States and Mexico. In this 
enormous extent of country local conditions have produced their 
expected results. As we go south this deer becomes a smaller 
and more delicate animal, the antlers simpler and lighter, until 
a Florida or Mexican specimen placed beside one from Maine 
or Canada would show a degree of divergence in size, color, 
and antlers clearly sufficient to constitute a separate species. As 
a matter of fact, these outlying types are recognized as sub- 
species, and I greatly doubt whether a hunter starting in Quebec 
or New Brunswick, and securing a continuous series of specimens 
as he passed down through Maine and New England, through 
the Adirondacks and Pennsylvania along the line of the Blue 
Ridge to the Gulf States, and thence to Mexico, could at any 
point in his travels find the locality where one group ends and 
another begins. As he progressed, one type would fade into 
another, new characters appearing in an ever-increasing percent- 
age of individuals. If, by some convulsion of nature, the deer 
of the Central States were destroyed and the Maine deer driven 
into Florida or Mexico—and such migrations have been common 
since terrestrial life first appeared—two valid species would exist 
in Florida. The Columbian Black-tail dwindling to the north 
into the Sitka deer furnishes a similar case. 
These examples are parallel in the case of the caribou. In- 
dividuals taken from widely distant points on the Pacific 
coast show widely different characters. So do deer taken from 
Maine, Florida, and Mexico. In the case of the deer, we know 
that intermediate types exist, and yet different sub-species are 
recognized from the localities just mentioned. In the case 
of the caribou we do not know whether intermediate types 
exist or not. If they do not exist, the question of the specific 
distinction of the forms described in this article may be consid- 
ered settled. If they are found to exist, their case will be analo- 
gous to that of the Virginia deer, and the so-called species will 
fall to the rank of sub-species or local races. 
The distinction between a species and a sub-species is founded 
on this very point. Several groups of animals, presenting char- 
acters of a certain value, and without intermediate forms, con- 
stitute as many different species. Groups of animals with the 
same characters, but fading imperceptibly into one another, are 
recognized as sub-species. Many types recognized now as sub- 
