OCR Text |
Show 242 ON RACES AND HYBRIDS AMONG THE SALMONID.E. [M rising two-year-old hybrid fishes, a very important fact must not be overlooked. Last season, 1883-84, it was observed that, although young Salmon-par at just over two years of age could fertilize the ova of Trout, the alevins were dropsical, and only about 100 out of 4000 survived. So the experiment was altered this season; and a young Lochleven Trout rising two years of age was employed to supplv the eggs which were milted from an adult of her own race. November 13, 1884.-About 500 eggs were obtained from a rising two-year-old Lochleven Trout, their average size being 0*17 of an inch in diameter (at 8 years old they are from 0*20 to 0*24 of an inch) ; these were impregnated from a male of average size and of the same race. The eggs were placed in box 124 b ; and it was observed that besides being small, they had a much thinner shell than had those of older fish. The eggs did very badly, and only about a dozen hatched. This experiment is of very great value, as tending to show that small eggs taken from young mothers have a deficiency of vitality in a similar manner to the milt of the young males. On December 9, 1884, about 400 ova were taken from a Howietoun Grilse and milted from a Lochleven Trout. The diameter of the eggs was 0*22 inch ; and they were placed in tray 108 b. Only about half the eggs appear to have been impregnated. December 13.-500 eggs were obtained from a dead Sea-Trout which had met its death from direct injury, a wound having extended into the ovary, and possibly water had then obtained entrance. To these eggs the milt of a Salmon par, reared at Howietoun, was added ; and they were deposited in box 84 c. The size of the eggs was 0*18 inch in diameter. Probably none will hatch. December 13, 1884.-650 eggs were obtained from a Sea-Trout, and having been impregnated from a Lochleven, they were placed in tray 84 b. The size of each egg was 0-18 inch in diameter. November 11, 1884.-About 12,000 eggs of the Lochleven Trout were milted from a Howietoun-reared smolt, and laid down in box No. 1. These eggs have done very well, only about 87 dead ones having been picked out; they hatched on January 28, and the young look well. In this experiment neither parent was under the third season. November 14, 1884.-About 800 eggs of the Lochleven Trout were milted from three Howietoun-reared pars and smolts. These eggs were placed in box 96 a. They hatched on February 5 ; the young are numerous, and appear to be very healthy. The remark on the age of the parents in the last experiment also may be applied to this. O n November 12, 1884, 1350 eggs of a Lochleven Trout were milted from a hybrid Char and Trout \ this hybrid being 8| inches in length. The eggs were placed in box 92 a ; only about 12 eyed, and out of these 3 embryos came to their full size, but had not sufficient vitality to burst their shell, dying unhatched. As a rule, the eggs appeared not to have been impregnated. On measuring 1 Proc. Zool. Soc. 1884, p. 586. |