86 



ME. F. DAY 01^ THE LOCH-LEYEN TKOUT. 



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, wall be slow 

 to believe that structural differences are not of much greater value. 

 Hence we must first inquire whether the number of these cascal 

 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 csecal pylori are from 60 to 80 in number. Sir J. Eichardson 

 found 73 in each of the three which he dissected, and Glinther from 

 49 to 90 ; and although in the description of the species the latter 

 writer says, "Csecal 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. C^cal p}/lori 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 in 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 and 49, I propose enumerating some which I have counted in 

 exaniples of this fish. Among males, in specimens varying from 7 

 to 20| inches in length, 1 have found tliem 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. 



