XXII BREEDING. 



HYBRIDS. 



It has been conclusively shown that hybrids are found both among marine 

 and fresh-water fishes, whether raised artificially or existing in a wild 

 condition, as might be anticipated when we remember that the milt of a male 

 might readily in water attain a proximity to the egg of one of another species 

 or genus. This has been more especially recorded among the carps 

 (vol. ii, page 157,- &c.) and the Salmonidce (vol. ii, page 80, &c.) "In 

 1869/' says Livingston Stone, " I crossed the yellow perch, Perca flavescens, 

 with the glass-eyed pike, Lucioperca, both percoids, using perch eggs arid 

 perch-pike milt. The' result was an embryo which continued to develop 

 till the seventh day, when the development suddenly stopped entirely, 

 although the embryo did not die. At this point it resembled the embryo of 

 the same age of the yellow perch proper." Fraisse asserts that he has been 

 able to effect by artificial fecundation a hybrid offspring between the trout 

 and theburbolt. Leuchart remarks upon having reared hybrids between the 

 female salmon and male trout, and from these he procured in due time milt and. 

 ova which were fertile. Other observers again have asserted that fertile 

 hybrids are only of occasional occurrence, and that eggs, produced from 

 them may be incapable of fertilization. The hybrids between the salmon and 

 trout instituted at Howietoun in 1879, have, so far as has been examined, 

 given sterile offspring. 



Some experiments were made by Sir James Gibson-Maitland, Bart., at 

 his fish-hatching establishment at Howietoun. On December 24, 1881, 

 20,000 eggs of the Lochleven trout were fertilized by salmon milt and 

 hatched on March 9, 1882. On March 13, 1884, there were 212 successfully 

 transferred to Craigend. Among these were six above 10 in. in length, but 

 some were as short as 2\ in., showing the great range of variation as to size 

 which maybe found in a single batch of young from the same parents and 

 kept under exactly similar conditions of existence. One examined in 

 August, 1884, was found to be a sterile female. 



On November 29, 1883, .4,500 eggs of the Lochleven variety of trout (of 

 the season of 1875) were milted from a par of the salmon raised at 

 Howietoun, and the mortality among the eggs was 1 in 46. But although this 

 was so, the curious fact remains that the milt of the par in this instance was 

 insufficient to impregnate the trout eggs, so as to produce young in a strong 

 and healthy condition, while weakly alevins either die or are next to useless 

 for stocking purposes. Although some thousands of the young emerged from 

 the eggs, all were at once seen to be suffering from what has been termed 

 dropsy or blue swelling of the yelk sac, which proved fatal before long to the 

 majority, only about 100 remaining in August. 



