34 Proceedings of Royal Roddy of Edinburgh. [sess. 
been a more appropriate title. This Tweed bull trout, otherwise 
known as the grey trout or round tail, is the S. eriox , as 
described by Yarrell, who, better I think than any other writer, 
seems to have recognised the rather distinct character of the fish. 
Gunther refers to Yarr ell’s S. eriox under S. cambricus, the sewen, 
or English and Irish equivalent of our Scottish sea trout ; and 
Day places the fish in the same category, with this difference, that 
he does not consider cambricus as specifically distinct from 
trutta. 
Without entering at length into the wide question of the 
genealogy of migratory and non-migratory trout, it is advisable to 
recollect both the apparently great differences which exist between 
what I prefer to call local races of trout, and the infinite gradations 
which certainly exist to join such local races with one another and 
with the typical sea trout or the typical brown trout. The result 
of transporting brown trout eggs to New Zealand has shown how 
rapidly change of environment will produce a fish which our 
British Museum authorities diagnose as typical sea trout 
(S. trutta). 
The late Sir James Maitland showed by different methods of 
feeding how Loch Leven trout could be made to resemble either 
S. fario or S. trutta ; the beautifully silvery trout ( fario ) of some 
of our West Highland lochs inaccessible to ascending fish; the 
characteristics of estuary trout, of the Orkney trout, or, let us say, 
of the creature usually described as Salmo ferox , are enough to 
show that either we must have a great many species, in accordance 
with the view adopted by Gunther, or, laying stress on the inter- 
mediate gradations, we must regard all trout as belonging to one 
species, and that a plastic, and therefore perhaps a comparatively 
recent species. The name S. eriox is as old as the thirteenth 
century. In 1824 Sir Humphrey Davy classed all our varieties 
under the name S. eriox ; but it being maintained in 1878 that the 
fish referred to by Linnseus was in reality the young of S. salar , 
the term eriox , , as applied to trout, was discarded, and by a process 
of gradual disentanglement from amongst the many specifically 
named creatures which in the interval had been described by 
naturalists, our present name of S. trutta has been brought into 
common use. 
