1 82 DARWINISM AND THE PROBLEMS OF LIFE 



The regulation of rivers has greatly reduced the 

 number of salmon. The time has gone when more 

 than a thousand could be caught at one spot in a day ; 

 when servants stipulated in their contracts that they 

 should not have to eat salmon more than twice a week. 

 In the Rhine it is gradually disappearing, as the mouth 

 of the river is almost entirely cut off by Dutch fishermen 

 at the time for coming up. In other rivers there has 

 been an artificial stimulation for the salmon population. 

 There are special places in which not only the eggs that 

 have been found are hatched, but the eggs are obtained 

 from the body of the ripe female by pressing it (also in 

 the case of the trout), and the sperm taken from the 

 male is poured over it. The young ones develop in 

 vessels full of water, that is kept fresh and circulating, 

 until they are big enough to make some resistance, 

 when they are put in the streams. In this way 

 an artificial substitute is found for the shallow 

 waters, and thousands of fishes are reared every 

 year. 



For a long time our fresh-water fishes were threatened 

 with a growing danger of extinction, until at last the 

 spread of knowledge enabled us to meet most of the 

 difficulties. Angling societies have been formed, and 

 fish-culture and protection are spreading more and 

 more. Angling is still common enough, and is re- 

 garded as a good form of sport. It is true that we 

 no longer see boats gliding over the river during the 

 night with torches in the bow, throwing a red light 

 over the slender form of the salmon-fisher and his 

 glistening harpoon ; but the angler sits under the trees 



