8 
BUIvIvETIN of the bureau of fisheries 
figured by Prof. McMurricli unfortunately were chosen from among the larger of those 
to be found on the cannery floor. 
The great majority of the Fraser River sockeyes have scales of the type above 
described, the nuclear area being small, of crowded rings, and sharply set off from the 
widely spaced summer rings which surround them. As we have shown, these have all 
developed from fish which migrated seaward as yearlings. A different type is repre- 
sented by plate xii, figure 22, in which it is seen that the nuclear area is much larger, the 
rings less closely crowded and widening gradually outward, until in extreme cases they 
merge almost imperceptibly with the succeeding summer rings. A scale of this type 
is figured by Prof. McMurrich (pi. iii) and is interpreted by him as indicating a fish 
“which went to the sea as a yearling in the second spring after hatching.” But the 
very reverse would seem to be the case. The large size and more widely spaced rings of 
the nuclear area indicate that growth in those individuals which spend their first year 
at sea is much more rapid than in those which remain in fresh water, and this is in 
accord with the few experiments which have been made with king salmon to determine 
that point. But more conclusive evidence of the history of these fish is found on com- 
paring their type of scale with the scales of the humpback and dog salmon, which 
always migrate seaward shortly after hatching and while still in the fingerling stage. 
The nuclear area of humpback and dog salmon is exactly similar to the sockeye type 
last described, being comparatively large in size and of widely spaced rings. Further- 
more, the king salmon, which migrates seaward partly as fingerlings and partly as year- 
lings, exhibits the same two types of scale shown by the sockeye, one with a small 
nuclear area of crowded rings, formed as can be demonstrated during the first year in 
fresh water, the other similar to the “sea t3'pe” of the humpback and dog salmon. 
While therefore we lack such direct demonstration as could be obtained by marking 
sockeye fingerlings on their seaward migration and observing on their return that the 
scales exhibit the “sea type” of nuclear area, there is j^’et sufficient evidence for the 
correctness of the theory to warrant us in accepting it. 
The possibility of distinguishing throughout their lives those individuals which 
passed to sea immediately after hatching from those which migrated as yearlings has 
opened up a wide field of investigation, upon which we have thus far barely entered. 
A certain practical difficulty is encountered at the outset. In the majority of cases 
there is no question to which type a given scale belongs. But among those of undoubted 
“sea type,” including humpbacks and dog salmon, as well as certain sockeyes and 
king salmon, there is found a tendency to the narrowing of a few of the rings immediately 
surrounding the nucleus, forming a sort of core to the nuclear area. (See pi. x, fig. 17.) 
The significance of this is in question, but we may perhaps hazard the conjecture that in 
such a case the individual tarried in fresh water or played back and forth on the tides for 
an appreciable time, during which growth was less rapid than in the majority which passed 
directly out to sea. Whatever the cause, this tendency to a slight central narrowing 
of rings of the nuclear area is of not infrequent occurrence in scales of the sea type, and 
is occasionally so pronounced as to simulate the smaller and least typical of what we 
may call for purposes of distinction the “stream nucleus.” In a small proportion of 
