80 
MR. F. DAT ON THE LOCH-LEVEN TROUT. 
number of these appendages than are usual in brook-trout until 
the present day this has been held conclusive evidence as to their 
specific difference from other forms. Many who would admit that 
variations in external colour or in that of the flesh, or even altera- 
tions in form, may be dependent on local surroundings, will be slow 
to believe that structural differences are not of much greater value. 
Hence we must first inquire whether the number of these caecal 
pylori are constant in the Loch-Leven race of trout, whether they 
ever vary in the brook-trout, and, lastly, if any facts can be pro- 
duced proving them to be inconstant. 
Among the local Loch-Leven forms we are told by Parnell that 
the caecal pylori are from GO to 80 in number. Sir J. Eichardson 
found 73 in each of the three which he dissected, and Gunther from 
49 to 90 ; and although in the description of the species the latter 
writer says, “Caecal pylori normally 60 to 80,” he instances seven 
females in the British-Museum collection as follows : — “ Females, 
from 12 to 18 inches long. Purchased, said to be from Loch Leven. 
Caught in April. Caecal pylori 65, 63, 60, 54, 54, 53, 49 ; 
vertebrae 58-59. These specimens have the pyloric appendages 
fewer in number than is generally stated ; yet these caeca are so 
wide — so much wider than in S.fario, that the reduction of their 
number has evidently been caused by a confluence of several 
caeca into one ” (Catal. vi. p. 101). 
From the foregoing statements it is evident that the number 
of these appendages is very variable, for we have them stated as 
being from 49 to 90. If, however, we turn to the writings of most 
authors who have counted the caecal pylori in S.fario, we find them 
enumerated as follows : — “ I have never found them to exceed 46 ” 
(Parnell, ‘ Fish Firth of Forth,’ p. 308). Thompson iu 1836 ex- 
amined the so-called S.ferox , and found in four examples 49, 45, 
39, and 36 (‘Nat. History of Ireland,’ iv. p. 157). Gunther 
among his other five non- migratory freshwater forms enumerated 
them as varying from 33 to 49. 
Having thus shown that these appendages in the Loch-Leven 
trout have been recorded as between 49 and 90, while in other non- 
migratory freshwater forms they have been found to be between 
33 ana 49, I propose enumerating some which I have counted in 
examples of this fish. Among males , in specimens varying from 7 
to 20| inches in length, 1 have found them as follows : — At Howie- 
toun, 8 examples of fertile fish averaged about 67 caecal appen- 
dages, founded on these numbers — 82, 75, 74, 73, 65, 62, 62, 48. 
