Man and Nature 427 



ascending falls 10-15 feet in height. Arrived on the spawn- 

 ing grounds in autumn the male excavates a little hollow in 

 the gravel of the stream bed, where the female deposits her 

 eggs, upon which the male sheds the "milt," after which 

 they cover them with gravel; and then the function of re- 

 production performed, which is the crowning act in the life 

 of either animal or plant, they float downstream to die. 



Perhaps nowhere else among animals is there shown a more 

 striking example of the influence of the sex organs upon 

 body form and general metabolism than in the male 

 salmon. In the spring he is a perfectly respectable looking 

 fish, but as summer advances and his sex glands ripen, the 

 jaws become greatly distorted, so much so in fact that in 

 some cases, it becomes impossible for the fish to close them. 

 Some of the teeth may disappear, while othere grow very 

 long. The body becomes compressed and assumes a distinct 

 hump in the back. 



The average number of eggs laid by a female salmon is 

 four thousand. If one-half of these developed into females 

 and reached maturity in four years, and if their progeny in 

 turn were all to reach maturity, one-half being females, this 

 rate of increase remaining constant from generation to gen- 

 eration, there would result in 32 years 256,000,000,000,000,- 

 000,000,000,000 salmon weighing 2,816,000,000,000,000,000,- 

 000,000 tons or 468 times the mass of the earth. 



Why is it that such increase is impossible? Let us see 

 what are some of the dangers which the salmon encounters 

 in its journey to its spawning grounds far distant from its 

 ocean home, and what those which await the eggs and fry. 

 Near the mouth of the salmon stream lurk the trollers seek- 

 ing to entice them with shining lure. Here too, and in the 

 broad reaches of the lower river, are the seiners, sweeping 

 the waters with their nets. Where the river begins to nar- 

 row so that a definite channel is established, the fish encounter 

 traps and weirs to stop them in their course; while higher 

 up, where the river narrows still more, the fish wheel bars 

 their progress. This is an ingenious device constructed some- 

 what on the principle of a Ferris wheel. It is placed where 

 the river is narrow and the current swift, and the river is 

 usually still further narrowed by means of a net or barri- 

 cade of some sort to oblige all ascending fish to pass through 

 the channel where the wheel is placed. Upon its rim are wire 

 baskets which catch the fish as they try to pass through 

 the narrow channel, and as the wheel turns empty the fish 

 into a spillway or sluice which carries them to a po<il where 

 the fisherman is waiting to receive them. Some of these fish 

 wheels are movable, being attached to the tail of a scow, if 



