PACIFIC HERRING 
247 
The chance of success with a fish as small and delicate as the herring would seem 
to be very slight without the evolution of some special technique for handling the 
fish while tagging, and of some lighter and less cumbersome form of tag. It may 
well be that further experiments with such a tag would succeed. 
Lacking successful direct methods, the widely used study of racial peculiarities 
becomes of primary importance. It is a well known fact that within the same species 
the isolation of particular stocks of fish tends to develop differences in their character- 
istics. These differences may exist in their physical structure or certain aspects of 
their life history, and may be too slight to detect in the individual but show in aver- 
ages. They may be entirely the direct result of environment, or they may be inherited. 
But if two such stocks were to intermingle freely, so that half in each locality would 
have originated in the other, then any such differences would necessarily vanish, as 
the averages in each case would be the same. A difference which could originate as 
the result of different feeding conditions for a few months would not have the same 
significance as a difference which would require isolation for generations, and which 
might be deeply seated in heredity. Nevertheless, the existence of differences between 
any two localities is prima facie evidence of the more or less complete lack of inter- 
mingling, and the more deep seated and clear cut the difference, the less the rate of 
intermigration must have been. The relative importance of the parts played by 
heredity and environment in causing the constancy of these differences between 
populations is a moot question, but the important point at issue is not the cause of 
such differences, but rather their existence and extent. 
Four of the structural characters were found to be of value — the counts of the 
vertebrae, of the dorsal rays, of the anal rays, and the measurements of the head 
length. The gill-raker count was taken on a number of samples, but it was found 
that accurate counts were not obtained under ordinary field conditions; and time in 
the laboratory was not available to make the enormous number of counts that would 
be required in order that their analysis might be of value. On a number of samples, 
measurements were made to the insertions of the dorsal and anal fins, but the varia- 
bility was found to be so great that enormous numbers would have to be measured 
before any value could be attached to the results. 
RACIAL SAMPLING 
Samples were obtained from the southernmost limits of the herring’s range, 
San Diego Bay, and from there in various regions west to the Aleutian Islands, and 
north to Golovin Bay in the northern part of the Bering Sea, an area covering 32 
degrees of north latitude and 45 degrees of west longitude. Within this great area 
was obtained a fairly complete chain of samples. They were taken at San Diego 
Bay; Monterey Bay; San Francisco Bay; Puget Sound; southern British Columbia; 
southeastern Alaska; Yakutat; Prince William Sound; Cook Inlet; the Kodiak- 
Afognak district; from Chignik, the Shumagin Islands, and Bclkofski Bay on the 
Alaska Peninsula, from Unalaska in the Aleutian Islands, and from Golovin Bay 
in the northern part of the Bering Sea. Unfortunately some of the samples, those 
from Yakutat and Belkofski Bay for example, are too small to give reliable averages 
for the characters. 
Besides having samples from many localities, it is also important to have sam- 
ples for more than one year from the same locality to study the amount of varia- 
bility to be found in the same character at the same place. In this regard samples 
are present for 2 years from Kachemak Bay, 3 years from Prince William Sound, and 
4 years from Shuyak Strait. 
