THE WHALEBONE WHALES OF THE WESTERN NORTH ATLANTIC. 3 
to the observation of stranded specimens in various stages of decomposition, in 
which the natural appearance and relationships of parts were partially or entirely 
obscured. 
Perhaps the greatest difficulty with which systematic cetology has to deal is 
the problem of individual variation. The extent to which individuals of the same 
species vary is enormous, and one unacquainted with this fact would be disposed 
to multiply species liberally, only to find after more extensive comparisons that the 
characters were slipping away. On account of the extraordinary individual varia- 
tion in this group of mammals, and the peculiar character of the material, it would 
seem the part of wisdom to treat the matter of species conservatively. To a 
certain extent the absence of definite barriers in the ocean permits the whales to 
range more widely than is usual with land mammals, and on this account geographi- 
cal races or sub-species are less likely to be formed. Still, from the observations of 
Scammon and others, it seems probable that species may in some cases be repre- 
sented in the ocean by distinct herds, which are distinguishable by various peculi- 
arities of size, form, proportion, and color. It is not certain, however, that these 
peculiarities may not be due to difference in sex and age. 
In the study of these animals, the question obtrudes itself whether groups of 
individuals belonging to certain species when separated from the remainder of the 
species by the width of a continent, can and do continue to reproduce their kind 
for an indefinite period without change. To decide the question negatively on a 
priori grounds, as is the tendency to-day, is, I think, unscientific. 
The present investigation, in so far as it reaches such questions, appears to 
support the view that detached groups of individuals of a species can perpetuate 
the characters of the species to which they belong for an indefinite period. 
To find a difference and erect upon it a species, is far easier than to prove that 
this difference is merely an individual variation or age distinction. Furthermore, 
species once established, though based on very unsubstantial characters, often 
acquire a standing which no amount of criticism can affect. Such “species,” it 
would seem, should have another name and be placed in a separate category. On 
the other hand, reluctance to accept species because they add to the length of the 
list, or to reduce them to synonymy without an examination of the material on 
which they are based, is to be decried. Between these two erroneous courses I 
have endeavored to steer in the present work. 
I appreciate that the conclusions arrived at here are little more than a confirm- 
ation of opinions held by Van Beneden and some other masters of cetology, but 
with few exceptions these opinions regarding American whales were not based on 
the examination of American material. If I am not deceived, they proceeded rather 
from the @ priori conclusion that it was not probable that other species existed 
than those frequenting European waters. 
With the exception of the type of Balena cisarctica, the types of the Ameri- 
can species of Cope and Scammon are figured here from photographs for the first 
time. Cope intended to monograph his species, but never brought the work to 
completion, 
