[1915 ICHTHYOLOGICAL NOTES 113 
forms are apt to be brought in with the currents. Although some of 
them linger around the mouth of the stream near by, others remain 
some distance away where the water is as salt as it is out in the open, 
hence it seems that salinity can have nothing to do with it. They are 
not hatched out very near by. So far as I am aware none are hatched 
nearer than the Nanaimo River, the mouth of which is four miles distant. 
That is quite a distance for the young salmon to come through the 
salt water before they are out of the alevin stage. 
When the yolk disappears there is no indication of any scales in the 
skin. About the middle of May when the fry are 40-45 mm. long, 
the scale makes its first appearance. It is round or oval, 0.14 to0.2 mm. 
in diameter, smooth and without rings. It is the nucleus of the large 
scale. In a week or two the first ring appears, soon followed by others, 
until by the end of June, when the fry disappears from this locality, 
there are 8 or 9 rings surrounding the central nucleus. 
Occasionally a few larger fish appear with the small ones, but I have 
not been able to obtain any of them. They are three or four inches 
long, and in all probability are dog salmon that have remained in the 
fresh water until the second spring instead of coming down the first 
spring. If one is to judge from the number that appear here, the pro- 
portion of second year fish is so low as to be almost negligible. 
III. DIAGNOSIS OF FISHES BY MEANS OF THE SCALES 
Plate X, figs. 30-35 
A system of identification of fishes by means of their scales has 
been advanced by Prof. T. D. A. Cockerell, but so far the system does 
not seem to have met with very great favor. Yet it is quite possible 
that the scale can be relied upon for identification purposes at least as 
fully as any other single characteristic if not as fully as all others com- 
bined. Since it has been discovered that the appearance of the scales 
may serve as a reliable indication of the age of the fish, the study of 
fish scales has become almost a science in itself, and there is no doubt 
but that it will add materially to the means of attacking the many 
problems connected with the life history. Two cases of personal interest 
may be quoted to show the value of the study of the scales in diagnosis. 
For some time after taking a special interest in the life-history of 
the herring, I knew nothing of the development between the time when 
the yolk was just absorbed and the time when the young fish was 6 cm. 
or over in length and had taken on the general appearance of the mature 
herring. On June 6th, 1913, there were numerous young fish, 35-40 mm. 
long, around the Government wharf on Gabriola Island. By June 12th 
s 
