MR. F. DAT ON THE LOCll-LETEN TROUT. 



87 



At Cowley, in Grloucestershire, one fertile male had 62, one 

 which was sterile 52. Among females, varying in leugth from 12 

 to 22 inches, the number of these appendages in 7 examples of 

 fertile fish averaged about 58, derived from the following numbers 

 — 66, 64, 62, 59, 57, 55, 45 ; while one large female from Loch 

 Leven had 47. As a rule these caeca appear to be larger in females 

 than in males, while in one of the latter a single one of these 

 tubes was abnormally shortened near the pylorus. 



The foregoing figures show a variation at Howietoun in the 

 number of these appendages, ranging from 48 to 82 in male fish, 

 and from 45 to 66 among female fish ; while in one male which 

 was fertile, examined in Gloucestershire, there were 62, and in 

 another, not so well fed, from the same locality, and sterile, there 

 were 52. In only one is the number seen to approach 90 (82) 

 as given by Dr. Gunther, and with that exception 75 was the 

 largest number counted, and from that down to 45, clearly 

 showing that this is an unstable character, prone to change, 

 and consequently unsuitable for discriminating species. Also 

 that, away from Loch Leveu, these appendages have diminished 

 in number, and still more so in examples from the ova hatched 

 at Guildford and reared in Gloucestershire, where the smallest 

 fish were sterile and had the fewest of these appendages. As to 

 the diameter of the caeca, the difference w^as not apparent, except 

 so far as I have mentioned above. 



Possibly the number of the caecal appendages may, under certain 

 circumstances, be found of value in ascertaining whether the food 

 on which the fish subsist is of such a nature that they will thrive 

 or deteriorate. 



If these appendages decrease when the fish are transferred 

 to other localities, it may be asked if instances can be adduced 

 where they have ever been found to increase in trout when 

 removed to better feeding-grounds or improved conditions of 

 life*. The eggs sent from the brook-trout of Hampshire and 

 Buckinghamshire by Mr. Frank Buckland and Mr. Francis 

 Francis to Tasmania have developed into a large race, in which 

 the caecal pylori seem to have reached the normal number of 52, 

 showing a considerable augmentation, and again proving the 

 number of these organs to be inconstant. 



Eespecting the vomerine teeth being in a single series in Loch- 

 * Since this paper was read (viz. in March 1887) young rainbow-trout 

 {Salmo iridens), 22 months old, raised at Howietoun, have been examined. In 

 California, whence the eggs were received, these fish are said to possess about 40 

 caecal appendages ; in one dissected at Howietoun I found 71. 



