52 SCIENCE SKETCHES. 
development of the organs of generation. High 
water on any of these rivers in the spring is always 
followed by an increased run of salmon. The 
salmon-canners think — and this is probably true — 
that salmon which would not have run till later 
are brought up by the contact with the cold water. 
The cause of this effect of cold fresh water is not 
understood. We may call it an instinct of the 
salmon, which is another way of expressing our 
ignorance. In general, it seems to be true that in 
those rivers and during those years when the 
spring run is greatest, the fall run is least to be 
depended on. 
As the season advances, smaller and younger 
salmon of these species (quinnat and blue-back) 
enter the rivers to spawn, and in the fall these 
young specimens are very numerous. We have 
thus far failed to notice any gradations in size or 
appearance of these young fish by which their 
ages could be ascertained. It is, however, prob- 
able that some of both sexes reproduce at the age 
of one year. In Frazer River, in the fall, quinnat 
male grilse of every size, from eight inches up- 
wards, were running, the milt fully developed, but 
usually not showing the hooked jaws and dark 
colors of the older males. Females less than eigh- 
teen inches in length were rare. All of either 
sex, large and small, then in the river, had the 
ovaries or milt developed. Little blue-backs of 
every size, down to six inches, are also found in 
the upper Columbia in the fall, with their organs 
of generation fully developed. Nincteen twentieths 
of these young fish are males, and some of them 
