346 ANNUAL OF SCIENTIFIC DISCOVERY. 



an unnatural agitation of the water and a washing of the banks, 

 against which the instinct of fishes does not teach them to provide, &c. 



" Artificial fecundation," says M. Quatrefages, " will remove all 

 these causes of destruction of the eggs ; and the employment of it 

 offers no difficulty whatever." The process employed by MM. Gehin 

 and Remy is of very simple and easy execution. In the case of the 

 trout for example, they proceed as follows : It is in November or the 

 beginning of December that the reproduction of trouts takes place. 

 To obtain the eggs intended for artificial fecundation, it suffices to 

 press slightly, from the front towards the rear, when the moment for 

 spawning has arrived, the abdomen of the female fish. The eggs 

 which fall should be received in a vessel of water ; and upon them 

 should be poured the milt or soft roe, obtained in an exactly similar 

 manner, by pressing it from the abdomen of the male fish into another 

 vessel of water. If these products have not arrived at maturity when 

 this operation is attempted, they will not flow out except under the 

 application of strong pressure. In such cases the fish should be kept 

 several days longer before operating this sort of forced accouchement ; 

 for neither the eggs nor the sperm can be profitably used in a state of 

 immaturity, and the lives of the parent fishes would be endangered by 

 any violent procedures. Immediately upon contact with the water 

 into which the sperm has been ejected, the eggs change color. Prior 

 to fecundation they are transparent, and of a yellowish color. As soon 

 as they are fecundated they become whitish, or rather opaline. A 

 trout of the age of two years only, and weighing about 125 grammes, 

 (4.40 ounces avoirdupois,) may furnish say 600 eggs ; a trout of three 

 years from 700 to 800 eggs. It is to be remarked that the milt of one 

 male suffices to fecundate the eggs supplied by half a dozen, or even a 

 greater number of females. 



MM. Gehin and Remy place the eggs thus fecundated on a bed of 

 gravel in tin boxes pierced with holes. These boxes are say six inches 

 broad and three inches deep, and can contain about one thousand 

 eggs each. They are placed in some little stream whose waters are 

 quick and clear, but not deep. They are partially interred in the bed 

 of the stream, and so arranged that the current will be perpetually 

 renewing the water which bathes the eggs ; for the agitation of the 

 water is necessary not only to assure the respiration of the embryos, 

 but also to prevent the formation of byssus or hair-weed, (conferves,} 

 which would rapidly appear and determine the death of the spawn if 

 the water were allowed to become stagnant. The development of 

 these embryos lasts about four months, and it is generally about the 

 end of March or in April that the exclusion or hatching takes place. 

 During the six first weeks the young trouts bear under the belly the 

 umbilical or vitelline vesicle which contains the remains of the nutri- 

 tive substance, analogous to the yolk of the eggs of birds ; and it is at 

 first by the consumption of this substance that the fry is nourished. 

 But when the absorption of this is completed, the little fish requires 

 other ailment ; and he must then be made to quit the box which has 

 served as his cradle, and allowed to swim about freely in the stream or 



