264 BRITISH FRESH-WATER FISHES 



The grounds for reckoning the trout of Loch Leven as 

 a distinct species (^Salmo levenensis) have been submitted of 

 late years to more searching analysis than has been applied to 

 the case of the ferox. Prolonged observation in the Loch 

 Leven hatchery and other similar establishments has tended to 

 show that, although pure Loch Leven trout maintain their dis- 

 tinctive outward character longer than most local varieties of 

 trout submitted to novel environment, yet the tendency is to 

 assimilate with trout from other waters. The excellent and 

 ■ abundant food in Loch Leven, enjoyed for centuries by the fish 

 in that favoured mere, has resulted in the establishm.ent of a 

 superior variety of trout ; but no such permanent changes in 

 structure have taken place as seem to me to constitute a species. 

 Loch Leven trout are distinguished by their somewhat slender 

 form compared with those in other waters, probably arising 

 from the rapidity of growth in consequence of stimulating 

 and plentiful nourishment. They are also more silvery than 

 most fresh-water trout, with less yellow along the sides of the 

 abdomen, and the spots are large and dark, without any scarlet. 

 The Gillaroo trout of some of the Irish loughs has been 

 classed by Dr. Giinther as a separate species, Salmo stomachicus, 

 on grounds which appear to me even less tenable than those 

 which sufficed for the Loch Leven trout. The sole constant 

 difference seems to be that the integument of the stomach is 

 three times as thick as that of an ordinary trout, which is 

 supposed to arise from this fish feeding to a large extent upon 

 shell-fish. Speaking with all diffidence, I submit that there is 

 nothing that has been ascertained about these trout to establish 

 them as more than well-fed, well-grown specimens of Salmo 

 fario, attaining the weight of lo lb., and seldom caught under 

 2 lb. in weight. The same Gillaroo represents the Irish giolla 

 ruadh, red fellow, indicating the orange and rosy tints of the 

 skin which distinguish it, when in fine condition, from the 

 silvery coated trout which are caught in the same lakes. 



I have already (page 257) ventured to express dissent from 



