806 



UNITED STATES, FISH- CULTURE IN THE. 



the water is introduced through a funnel- 

 shaped glass tube upon the bottom, and thence 

 passes upward through the eggs. Clark's hatch- 

 ing-jar is similar to Chase's, differing mainly in 

 having upon the bottom a metal cone to re- 

 ceive the funnel-shaped end of the supply- 

 tube, which is kept from contact with the 

 cone by slight projections on the inner surface 

 of the tube. The "Wilmot jar was subsequent 

 to and in imitation of Chase's. 



For hatching adhesive eggs, one of the ear- 

 liest forms of apparatus employed was that de- 

 scribed by Christian Lund, in Norway, in 1761. 

 This was a box charred on the inside and lined 



LUND'S Box. 



with bushes, its sides being perforated. This 

 box was placed in shallow water near the bank 

 of a river, and in it were confined the parent 

 fish when about to spawn. The eggs adhered 

 to the bushes and were left to hatch in the 

 stream, but the fish were removed. Subse- 

 quently the sides were made movable, so that 

 they, with the egg-bearing bushes, might be 

 transported. The Lund principle of hatching 

 adhesive eggs, with some modifications, is still 

 extensively applied in many countries. In 

 1876 James Ricardo, of New Jersey, success- 

 fully used for hatching smelt a rectangular box 

 with a hinged cover, and perforated ends fur- 

 nished with wire-cloth, the inside provided 

 with twigs to which the eggs became attached. 

 This box was placed in a strong current in the 

 river. In 1878 Mr. Frank N. Clark employed, 

 for hatching eggs of the sea-herring, a rectan- 

 gular box containing numerous oblique grooves 

 in the sides, in which were placed panes of 

 glass resting alternately on the bottom and at 

 a distance of a half-inch above the bottom. 

 The eggs were taken, impregnated, and hatched 

 on these panes. The current of water passed 

 over the top of the first pane, under the second, 

 over the third, and so on. Adhesive eggs may 

 be manipulated with great ease by the use of 

 the McDonald egg-reel, a contrivance by means 

 of which they are attached to cotton cord, to 

 facilitate transporting and hatching. A frame 

 23 inches high and 14 inches wide supports a 

 reel 12 inches long and 10 inches broad. Be- 

 neath the reel is a square box containing at the 

 bottom a ball of twine, and receiving in the 

 top a funnel 6 inches in diameter. One end 



of the twine passes through the funnel and is 

 fastened to the reel. The eggs are placed in 

 water in the funnel, and, as the twine passes 

 through them upon moving the reel, quantities 

 of them adhere to it and are drawn upon the 

 frame. 



Methods of Treating Eggs. For. the fertilization 

 of eggs two methods have been employed the 

 "wet" and the "dry." It was at first sup- 

 posed that the eggs must be received in water, 

 some culturists even taking the trouble to press 

 them out under the water, and the milt was 

 treated in the same manner. This, the " wet " 

 method, was superseded by the " dry" method, 

 which some claim was first practiced in 

 America ; it was, however, first published 

 by Vrasski, a Russian, in 1856, and is now 

 used almost universally. By this method 

 the eggs are received in a dry pan, and the 

 milt is distributed directly upon them. It 

 is claimed that 99 per cent, of the eggs have 

 been impregnated by the " dry " process. 



The method of impregnating fish-eggs in 

 general is as follows : Having found a fe- 

 male from which the eggs will flow freely 

 upon slight pressure, grasp her firmly with 

 the left hand around the tail, pressing her 

 head closely against your body ; then with 

 the right thumb and forefinger exert a 

 gentle pressure on the opposite sides of 

 the belly, beginning at the breast-fins and 

 continuing about to the middle of the length. 

 The eggs should be received in a dry pan. 

 By similar treatment of the male, squeeze 

 jets of milt upon the eggs, swaying the pan 

 gently to and fro, to insure commingling of 

 the two elements. (See engraving, page 796.) 

 Add a little water from time to time un- 

 til the eggs increase in size and feel hard to 

 the touch. All foreign substances, such as 

 scales, dirt, blood, etc., must be carefully washed 

 off. The period of incubation of fish-eggs 

 depends upon the temperature of the water, 

 increasing with a rise and diminishing with a 

 fall. In the treatment of eggs of salmon and 

 white-fish, artificial refrigeration is employed to 

 retard development and protract the hatching- 

 season. In a state of nature the white-fish sea- 

 son is especially brief, but by refrigeration, 

 Frank N. Clark, of the United States Fish Com- 

 mission, has extended it materially, and is now 

 developing three times as many eggs as he 

 could without refrigeration. Sir James Mait- 

 land has taken advantage of another principle 

 of retardation. By giving the females an abun- 

 dance of substantial food when the pairing- 

 season approaches, he can perceptibly hasten 

 the date of spawning, and by feeding them 

 sparingly he can materially retard that event. 

 In this way he extends the hatching-season of 

 salmonoids considerably. 



The production of shad has been greatly in- 

 creased by Col. McDonald's discovery of the 

 method of transportation of eggs in the dry 

 state. The eggs, after fertilization, are placed 

 in trays with a wire-cloth bottom and covered 



