BULLETIN OF THE UNITED STATES FISH COMMISSION. 397 



{Taenia solium) 40 millions. Most of these millions of eggs are destroyed 

 because numerous and regularly recurring difficulties prevent their 

 development. It is highly probable that this enormous production of 

 eggs has been brought about by these very difficulties. Only the most 

 fertile kinds bequeathed their qualities from one generation to the other 

 in the struggle with the numerous destructive influences, because they 

 furnished a larger number of combatants than the less fertile kinds, 

 which therefore finally died out. 



Where would all the flounders find food and room, if all the eggs of 

 the mature spawners were destined to become fish % It is only by the 

 circumstance that the mature females lay so many eggs that the full 

 amount of flounders allowed by the quantity of food obtained, and the 

 life in common of all the members of their community, can be main- 

 tained. How can we demand that this amount, exposed to so many 

 natural enemies, should not be decreased by our destroying milliards of 

 eggs before they have been laid? 



We can do this without diminishing the amount if we remove the nat- 

 ural causes by which eggs and young animals are destroyed. This is 

 successfully done in artificial oyster-culture in Holland and France, 

 where the oyster spawn is, in suitable places, made to adhere to bricks, 

 and the young oysters are protected in boxes and artificial basins 

 against enemies and other hurtful influences, and allowed to grow to 

 maturity in places where there is plenty of food. 



If we desire to obtain permanently from our coast waters more use- 

 ful salt-water fish than can be developed under the natural conditions 

 of life, we must protect their eggs and their young according to the 

 same rules which are followed in the artificial culture of oysters and 

 fresh-water fish. We might possibly construct basins for flounders in 

 suitable places on the coast, where artificially-impregnated eggs, pro- 

 tected from enemies, would develop in much larger quantities than in 

 the open sea. Suitable food for the young fish might be introduced by 

 frequently renewing the water from the sea before the young fish are 

 allowed to go into it. 



If it is possible to start such flounder hatcheries, or similar ones, for 

 stocking the waters on our Baltic coast with flounders, their construc- 

 tion, support, and superintendence would cost so much that before they 

 can be constructed an attempt will have to be made to carry on the 

 flounder fisheries in such a manner that they will permanently yield 

 the maximum quantity of fish which they can yield under the existing 

 natural conditions ; and this they can only do permanently when no 

 small fish are caught at all, and, during a certain protected season, no 

 full grown ones. The fishermen themselves must learn to know this, 

 and for their own advantage act accordingly. 



I believe that these explanations have made it sufficiently plain that 

 the number of animals within a given territory is not dependent on 

 accidents, but is determined by the co-operation, according to fixed 



