342 



EVOLUTION AND ANIMAL LIFE 



of the anadromous instinct is found in the king salmon or 

 qumnat {Oncorhyiichus tschaivytscha) of the Pacific Coast. 

 This great fish spawns in November, at the age of four years 

 and with an average weight of twenty-two pounds. In the 

 Columbia River it begins running with the spring freshets in 

 March and April. It spends the whole summer without feeding 

 in the ascent of the river. By the autumn, the individuals 



Fig. 203. — Giant gall of the white oak (California) made by the gall fly, Andricvs cali- 

 fornicus; the gall at the right cut open to show the tunnels made by the insects in 

 escaping from the gall. (From photograph.) 



have reached the mountain streams of Idaho, greatly changed 

 in appearance, discolored, worn, and distorted. The male is 

 humpbacked, with sunken scales and greatly enlarged, hooked, 

 bent, or twisted jaws, w^ith enlarged doglike teeth. On reach- 

 ing the spawning beds, which may be a thousand miles from 

 the sea in the Columbia, over two thousand miles in the Yukon, 

 the female deposits her eggs in the gravel of some shallow brook. 

 The male covers them and scrapes the gravel over them. 

 Then both male and female drift tail foremost helplessly down 

 the stream: none, so far as certainly known, ever survives the 

 reproductive act. The same habits are found in the four other 

 species of salmon in the Pacific, but in most cases the individuals 

 do not start so early nor run so far. The blueback salmon or 

 redfish, however, does not fall far short in these regards. The 

 salmon of the Atlantic has a similar habit, but the distance 

 traveled is everywhere mucli less, and the hook-jawed males 



