1166 FISHERIES OF THE UNITED STATES. [12] 



To enforce these laws would, however, render necessary a large force of 

 fish wardens. 



" The policy of the United States Commissioner has been to carry out 

 the idea that it is better to expend a small amount of public money in 

 making fish so abundant that they can be caught without restriction 

 and serve as cheap food for the people at large, rather than to expend 

 a much larger amount in preventing the people from catching the few 

 that still remain after generations of improvidence." 



The first experiments in fish-culture by Dr. Garlick were conducted 

 in an ordinary trough filled with running water, the bottom being cov- 

 ered with gravel, so that the conditions might approximate as nearly as 

 possible to the natural conditions of the river bed. As fish-culture 

 has become more extensive experiments have been made in the arti- 

 ficial propagation of numerous other species, which have necessitated 

 the invention of apparatus of an entirely different character. 



The eggs thus far hatched may be referred to one of four classes, viz : 

 (1) heavy eggs, (2) semi buoyant eggs, (3) adhesive eggs, and (4) float- 

 ing e.2gs. Each of these classes requires apparatus adapted to itself, 

 and that suited to one is frequently entirely unfit for another. 



The apparatus for heavy eggs has numerous modifications, depending 

 upon the direction of the current through the eggs. All of the older 

 forms required a horizontal current, but the more recent ones have the 

 eggs arranged in trays, one above the other, with the current passing 

 either upward or downward through them. 



Apparatus for semi-buoyant eggs has undergone considerable change. 

 They were for a time hatched with fair suciess on trays with a down- 

 ward current of water, but the use of this apparatus is now entirely 

 discontinued. The present forms are floating boxes for utilizing river 

 currents, submerged boxes for utilizing wave action, closed vessels for 

 utilizing head or hydrant pressure, and mechanical apparatus. The 

 third named is unquestionably the most satisfactory, as it is more eco- 

 nomical and more convenient than the others. This form has undergone 

 numerous modifications to make it automatic, and is now perfected so 

 that the dead eggs pass off with the waste water and the young fish are 

 collected in aquarium receivers. 



Several forms of apparatus have been invented for adhesive eggs. 

 The first were copied from Sweden, consisting of wooden boxes, pro- 

 tected by wire netting, containing twigs covered with eggs and placed 

 in the open streams. The most important form consists of a wooden 

 trough with glass plates placed transversely and extending entirely 

 across it, fitting in grooves at the side, each alternate one being a little 

 above the bottom of the trough, so that the current passes over the first, 

 under the second, over the third, &c, on its way through the trough, 

 thus furnishing a constant current around each plate. The eggs are 

 placed upon the glass plates, which can be easily removed to be cleaned 

 of any sediment that may have gathered upon them. No apparatus has 



