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Show 378 MR. F. DAY ON RACES AND HYURIDS [May 20, sac, showing the existence of two coats, separated one from another by an accumulation of clear fluid. Under a strong glass there appeared to be a want of vitality in the fish, the pulsations being feeble, the activity of the heart being less than in more healthy forms, and a deficiency of red corpuscles in the blood. Due to this dropsical distension, the pectoral fins were much impeded in their movements, which is very material, because in the young fish these fins are in constant motion, in order by keeping up a continuous current to help the gill-covers in aerating the blood at the gills, for the gills at this early period of life are partially uncovered, although not free as seen in fcetal plagiostomes. Another experiment made at the same time leads to a corroboration of my belief that the milt of these young Salmon-parr is deficient in marital powers, for, as I previously remarked, 1000 eggs of the common Brook-trout were milted from one of these Salmon-parr which had been dead a few hours. The result in this instance has been that not one single egg was fructified. Only 3 eggs turned white in December, 3 in January, and 15 in February, or a total of 21 ; and on March 12 the remainder were still quite clear, but without a sign of an embryo within. It has been remarked at Howietoun, that eggs from young mothers are subject to a greater percentage of deaths than those taken from older fish, and this raises the conjecture that, similarly, the marital power of milt from young males may possess less fertilizing properties than that obtained from older parents. On March 26, Sir J. Gibson-Maitland sent me specimens of these hybrids, the largest of which was 0*7 inch in length, and the comparative size of the dropsical swelling, as may be seen from the diagrams on the wall, or the examples on the table, had considerably augmented in size. From this period these fish commenced dying off, and by May 15 none of those which suffered severely with dropsy were left, but about 400 that from the first had not been so weakly as the others. One of these I received alive from Howietoun, sent in a small glass bottle of water (containing rather less than half an ounce) through the post ; after arrival it lived 43 hours in a tumbler. Its length was 0*8 of an inch, or the same as was the average of those I measured on March 12, when nearly one month old : the specimen is on the table. The other experiments I will now briefly chronicle. On November 29, 1883, 3695 (formerly printed 2695) eggs of Salmo fontinalis were milted from a parr of Salmo salar. In December, 144 dead eggs were removed, during January 1527, and in February 401, or a total loss of 3372 ova. On March 12, 1884, 7 were alive, but not in a satisfactory condition. On November 15, 1882, 2000 ova from a Lochleven Trout were milted from a Salmo fontinalis ; on November 29, 1883, 150 were estimated to be alive, but this must have been too low a number- 250 seems to be more probably nearer the mark. These have been kept in a large wooden box, rather exposed to the east, but still had done comparatively well up to this time. On this day, March 12, |