AGRICULTURAL ZOOLOGY. 345 



" that the Natural History Society of New Jersey are prepared to make, to the three States 

 of New York, New Jersey, and Penns3 T lvar±ia, an offer to restock the Hudson, Passaic, Rari- 

 tan, and Delaware rivers, with salmon fry; provided the legislatures will jointly, or severally, 

 pass such laws for the preservation of the fish, until they shall become fully established in 

 those waters, and forever during spawning season, including the removal of all obstacles to 

 their free ingression and retrogression to and from the salt water, as shall be deemed suffi- 

 cient ; the society asking no privilege, or remuneration, beyond the actual expenses of pro- 

 viding and transporting the fry." 



IThere are two ways in which fish may be propagated artificially in any quantities. The 

 one is by taking the breeding fishes alive, male and female, previous to their depositing their 

 spawn, in the gravel shoals of their native beds, and compelling the female fish, first, by a 

 gentle pressure of the hands upon her sides, to deposit her ova on a layer of gravel, in a 

 box suitably prepared for the purpose, covered with a wire grating, and provided with suitable 

 apertures, similarly guarded at one extremity to admit the influx and afflux of spring water 

 from a source of proper temperature, without which the ova cannot be matured. This done, 

 the male fish is, by a similar treatment, forced to emit his milt over the female ova on the 

 gravel, which are thus impregnated, when the box is placed so as to receive a constant current 

 of aerated running water, subjected to which the eggs are hatched, and the young fish 

 excluded in a space of 



114 days, when the temperature of the water is 36° 



101 " « " " 43° 



90 " " " " 45° 



The experiments by which these facts were arrived at were performed in the open air, in 

 natural streams, liable to the ordinary influences of the atmosphere and weather. 



The second method is the mixing in the same manner of the milt of the male with the ova 

 of the female fish, taken out of the bodies of fish recently dead. It is proved, indubitably, 

 that the eggs thus prepared, and similarly subjected to the flow of aerated spring water, will 

 produce living fish. This method has been largely put into practice in France, where exten- 

 sive waters have been stocked with both fresh and salt-water species, although it is certain 

 that sea-fishes, if excluded from salt water, lose much of the characteristic excellence of 

 their flesh ; while it is doubtful, at least, whether they have the power, under those circum- 

 stances, of reproducing their species. 



Both these methods, however, presuppose the possibility of having either the live fish 

 taken on the spot, when in condition for the immediate deposition of its ova, or the dead fish, 

 in the same condition, immediately, or within a few hours, after the capture — since it cannot 

 be expected that the vitality of the ova would long survive the death of the parent animal. 

 These conditions, therefoi'e, render it indispensable that the experiments should be performed, 

 and the system of breeding carried on, where the living fish or the dead fish immediately out 

 of che water can be readily procured ; that is to say, in the immediate vicinity of salmon 

 rivers. This would, of course, render it necessary to form breeding establishments at a dis- 

 tance from this section of the country, and to provide for their subsequent transportation. 

 Fortunately, however, this difficulty is obviated by another peculiarity of the young salmon, 

 which the Natural History Society of New Jersey propose to turn to account in their scheme 

 of restocking the rivers named above. On first emerging from the membrane in which it 

 was enclosed, or being hatched, the young fry has the yolk of the egg attached to the ante- 

 rior part of the abdomen, immediately behind the gills, and for the first twenty-seven days 

 of its existence takes no manner of food externally, being supported wholly by its absorption 

 of this nutritious substance. At the end of this period, it has attained the length of about 

 three-quarters of an inch, and is enabled to forage for itself and live on the prey which it 

 captures, which is identical with that of the trout. During the first twenty-seven days of 

 its life, therefore, the young salmon may be enclosed in bottles, casks, or any other utensils 

 of the like nature filled with water, which it is not necessary to change during that period, 

 and may be transported any distance which can be compassed by steam within that time. 

 If then turned out into rapidly running, aerated streams with gravel bottoms, suited for the 

 nutriment of trout, it will remain in those waters until the middle of the May of the year 



