406 ilR. F. DAT ON JBEITISH SALMONES. 



pink. It is clear, from tlie foregoing differences in colour in the 

 flesh of an unquestionably single species of Sahw, that it may be 

 pearly white, perfectly pink, or of a gamboge colour, but equally 

 good for the table, the fish being in good condition in all the 

 several forms. 



The external colours of these fish (omitting such as are due to 

 age, condition of health, or the breeding-season) vary in a very 

 wide manner, in accordance Avith the localities they inhabit, the 

 nature of the soil or bottom of the Avater, the rapidity or the 

 reverse of the current, the extent and depth of the Avater, as 

 well as the food, light, and temperature. Clear Avater in rapid 

 rivers or lakes, especially when the bottom is pebbly, often con- 

 tains somewhat silvery fishes A\dth black X-shaped marks. Many 

 experiments have been made, showing hoAv rapidly one of these 

 fishes may change colour. " Put a living hlacJc burn-trout into a 

 Avhite bason, and it becomes AAdthin half an hour of a light colour. 

 Keep the fish living in a white jar for some days, and it becomes 

 absolutely AA^hite ; but put it into a dark-coloured or black vessel, 

 and although on first being placed there the Avhite-coloured fish 

 shows most conspicuously on the black ground, in a qu.arter of an 

 hour it becomes as dark-coloured as the bottom of the jar, and 

 consequently difficult to be seen " (St. John, ' Natural History 

 and Sports in Moray,' p. 25). All practical anglers know how 

 trout of very different colours may be captured from contiguous 

 streams, or from ponds into AA^hich they have been introduced, 

 from what they Avere when originally placed there. " Unques- 

 tionably," observes Stoddart (' Angler's Companion,' 1847, p. 3), 

 " there exists no species of fish which, judging of it by the exter- 

 nal marks, holds claim to so many varieties as the common fresh- 

 AA^ater trout. In Scotland almost every lake, river, and streamlet 

 possesses a breed peculiar in outAA^ard appearance to itself." 

 Jurine, respecting the fishes of the Lake of Geneva, observes 

 that the common trout, salmon-trout, lake-trout, river-trout, the 

 alpine trout^ &c. are all referable to differences of sex, age, 

 season, the nature of the Avater, food, light, &c. (Mem. de la Soc. 

 de Phys. et d'Hist. Nat. de G-eneve)> 



If some trout esteem food AA^hich causes their flesh to be tinged 

 Avith red, Avhile others in the same Avater appreciate a different 

 sustenance, and consequently are not thus tinged, if the Gillaroo 

 eats shells, occasioning thickening of the middle coat of its stomach, 



