3/8 MR. F. DAY ON RACES AND HYBRIDS [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 foetal plagiostomes. 



Another experiment made at the same time leads to a corrobora- 

 tion of my belief that the milt of these young Salmon-parr is defi- 

 cient 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 iu 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 with- 

 out 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 ferti- 

 lizing properties than that obtained from older parents. 



On March 26, Sir J. Gibsou-Maitland sent me specimens of these 

 hybrids, the largest of which was - 7 inch in length, and the com- 

 parative size of the dropsical swelling, as may be seen from the dia- 

 grams on the wall, or the examples on the table, had considerably 

 augmented in size. From this period these fish commenced dying 

 ofl 7 , 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 - 8 of an inch, or the same as was the 

 average of those I measured on March 12, when nearly one mouth 

 old : the specimen is on the table. 



The other experiments I will now briefly chronicle. Ou Novem- 

 ber 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, 



