252 BRITISH FRESH-WATER FISHES 
migratory trout of Great Britain. Dr. Gunther has catalogued 
four separate species under the titles Sa/mo trutta, S. cambricus, 
S. gallivensis, and S. brachypoma. On the other hand, Dr. Day, 
while naming two—S. trutta and S. cambricus—considers that 
the second is but the southern variety of the first. This is far 
more nearly in accordance with the observation of unscientific 
men accustomed to handle and sell these fish, but there remains 
this difficulty in accepting Dr. Day’s definition, that, whereas 
his Salmo cambricus must be taken as intended to include what 
is known in most parts as the bull-trout (S. eriox of Linnzus), 
it is difficult to rate as a southern form a fish which is 
peculiarly abundant on the coasts of Northumberland and 
Berwick. 
The shape of the gill-cover, the arrangement of teeth on 
the vomer, the number of cecal and pyloric appendages, the 
number of vertebra, and the general appearance of these fish— 
all of which are relied upon to indicate species—are so much 
subject to variation, and blend so imperceptibly into inter- 
mediate forms, that it is safest to hold judgment in suspense 
for the present, and for practical purposes to maintain those 
lines of distinction about which there is no manner of doubt in 
the minds of experienced fishermen. It seems unnecessary to 
go so far as H. Widegren did in 1863, and as later Continental 
authorities have followed him in doing—namely, to reduce all 
the European Sa/mones to two species, S. salar and S. trutta, in 
the latter of which he would group all trout, whether regularly 
migratory and maritime in habit or not. Even if the dominant 
races of British trout be ultimately proved to be convertible, 
under uniform treatment and environment, to a single type 
(which I am far from denying to be possible, and even 
probable), it seems almost pedantic to refuse specific titles to 
thoses types which are perfectly distinguishable by appearance 
and habit, and which have not yet been proved to be inter- 
changeable. I shall therefore venture to define as the salmon- 
trout (Sa/mo trutta) the fish known in Ireland as the white 
