HYBRIDS, LOCAL RACES AND VARIETIES. 7 



As to the varieties and hybrids of trout. If, as seems probable, we merely possess 

 one very plastic species subject to an almost unlimited amount of variation, that 

 its largest race is found in the ocean, while in order to breed it ascends streams, 

 but usually (to which there are many exceptions) not so far as the salmon, unless 

 it permanently takes up its abode in the fresh waters, we at once obtain a clue to 

 the characters of the various so-called species, and relegate these difEerent trout 

 to a single form, in which numerous local races are to be found.* *This also 

 accounts for the hybrid theory, or numerous hybrid trout stated to exist in our 

 waters ; for they should be regarded as really changing local races, as to whether 

 they are assuming a fresh-water existence from a saline one, or vice versa. 



Here it will be necessary to slightly digress for the purpose of discriminating 

 between local races or varieties and species, because what one naturalist considers 

 a variety another may look upon as a species. Two primary characters have been 

 selected as demonstrating the true position of a specimen, either the morphological 

 or that relating to its structure and development ; or secondly, the physiological 

 as relating to its functions. Even within the limits of a single species no two are 

 found to be exactly similar, but a tendency to diverge from the original type 

 appears to exist, which power of divergence is in such a direction as will be most 

 likely to preserve and increase useful variations. For it seems to have been 

 conclusively shown that there exists a law in animal life of an hereditary tendency 

 to follow the specific type, while there is likewise a law of variability by 

 adaptation which is destined to modify every organism so as to fit it for new 

 conditions of existence. Owing to a knowledge of this latter tendency, by means 

 of judicious selection and breeding from individuals that are possessed of some 

 desirable variation, such may become permanent through future generations :t 

 while natural selection (perhaps assisted by some as yet unknown factor) would 

 similarly tend to favour the continuation among' wild races, of forms which 

 possess variations favouralde to the life of the fish and thus produce and continue 



* The clescenclanls of the common brook trout sent to Tasmania have shown in most localities 

 very great disposition to vary. Mr. Arthur informed us that " In the Shag river the largest trout are 

 near the tideway, and small trout numerous above. In the Leith the large trout are only found 

 during spawning time." Also, " That as large trout are not now seen in the Leith except during 

 winter, they must live in the brackish water at its mouth, or in the bay itself, for nine months 

 out of the twelve. And this is further borne out by the fact of many large fish being netted by the 

 fishermen in the bay with the characters, more or less, of the brown trout." In short, the brook 

 trout are here migrating seawards, and becoming anadromous. 



A trout, Salniofarii), of 2.5 lb. weight, 32 2 in. long, and 2 ft. in girth, from Wairnakirri, New 

 Zealand, as silvery as a salmon and marked with X-spots, was taken by Mr. Fan- to the British 

 Museum, where it is preserved in spirit. In the same river the trout caught previous to 1878 

 were marked with red spots, but they are never seen there now (TJie Field, Dec. 20th, 1880). 

 Thus we are able to trace in the Antipodes not merely changing colours, but varying habits in 

 the descendants of the non-migratory brook trout, which in a few generations has assumed more 

 or less of the sea dress and anadromous habits of the European sea trout. 



Eespecting the char, ,S'. tiljiiitus, we are told by Dr. 0. Renter, in his Fishes of FinlamI, 

 tliat it is met with on the coast of the Arctic Sea and in the rivers, which they ascend 

 to spawn ; but in Sweden it is known exclusively as a fresh-water fish, while it is quite clear that 

 the American trout, Salmo fviiti)!!]!!:!, belongs to this division of the genus Sahno. Professor 

 Jordan observed the common Rocky Mountain trout, S. 2>i>ri>ur<itus, is so known when taken in 

 rivers and brooks, and as salmon trout when taken in the sea or river's mouth ; for sea-run 

 specimens are more silvery, the only difference being temporary, and dependent on the water and 

 possibly on the food. {IJtdl. U.S. Fish. Com. 1885, p. 310.) The British char has been said to 

 have descended to the sea in ^Yales after it had been driven out of Llanberris Lake by poisoned 

 water, and Mr. Jackson observed upon two which had escaped from a fresh-water tank in the 

 Southport Aquarium and were captured many weeks afterwards by some boys fishing in the 

 contiguous salt water, there does not seem any more reason why char should not be of marine 

 origin than trout or salmon, while he would be a bold reasoner who could maintain that char, 

 trout, and salmon are descendants from more than one ancestry ; that, in short, the salmon was 

 a marine and the trout and char strictly fresh-water forms. 



f The experienced fish-culturist is aware how varied are the changes observable in some 

 piscine forms, as for instance in the gold carp, Carassiiis anratiis, wherein may be found 

 differences in form, proportions, colours, and in many ways, but all sprung from a single original 

 stock and capable of being reproduced by artificial culture. Similarly the various races of 

 common caqj, Cy^cfjiifn carpio, as the leather carp, the mirror carp, &c , are merely local races 

 of one species, and possibly some of our Salmonida; have similarly shown local peculiarities which 

 mistaken zoologists have believed to constitute species. 



