l8o DARWINISM AND THE PROBLEMS OF LIFE 



along the shore ; if water was drawn at this time, it 

 was sure to contain numbers of small eels. As the 

 large locks now hinder the advance of the young 

 eels, fish-ladders have been fixed in the wood in most 

 places — that is to say, bands of moss that remain always 

 moist, and enable the tiny animals to climb up. The 

 higher they penetrate, the more the males hang back ; 

 many believe that the fresh water turns the young, 

 sexless animals into females, but that has not yet been 

 proved. The young mature quickly, and feed by 

 preying on fishes, snails, insects, and carrion ; also on 

 crabs when they are removing their shells and are still 

 soft. Eels have often annihilated all the crabs in a 

 given locality. It is a mere myth, of course, that the 

 €el goes on pea-fields and feeds on the plants. 



The salmon acts in the opposite way from the eel. 

 It spawns in fresh water. In the sea it lives on small 

 fishes of all kinds, and becomes very fat. When the 

 ice disappears from the rivers, the salmon gather at 

 the mouths in companies of thirty or forty, and remain 

 for a time in the brackish water, so that the salt-water in 

 their bodies may be gradually washed out by the fresh ; 

 too sudden a transition would be fatal to them. They 

 then press steadily up stream. All obstacles are over- 

 come. Weirs and rapids are taken in leaps that some- 

 times reach the height of four yards. Only very high 

 waterfalls stop them. The young are in front, then the 

 older females ; these are followed by the younger males, 

 and the rear is formed of the older males — though an 

 old and strong fish seems to lead them, as a rule. 

 During the whole time they are in fresh water the 



