FISHING AT HOME AND ABROAD 

 upon certain modifications of internal structure and external features, 

 some ichthyologists have tabulated as many as twenty-four different 

 species. Scientific opinion, however, has now veered in the direction 

 of recognizing all the European non- migratory trout as more or less 

 permanent varieties of the single species of Salmo fario. The term fario 

 has no distinct significance; it is a word used by the late Latin writers 

 Ausonius and Isidorus to designate a fish which was probably a trout. 

 Were it not for the inconvenience of changing a name so long established, 

 a far better title for this most protean of fishes would be Salmo variabilis , 

 which was actually applied by Lunel to include the four forms — so-called 

 species — of trout inhabiting Lake Constance. 



The distinctive features formerly relied on to indicate separate species 

 have proved to be utterly untrustworthy. Take, for instance, the number 

 of pyloric caeca, which are secreting appendages on the intestine. Parnell, 

 Yarrell and Couch chiefly relied upon the superior number of these in the 

 trout of Loch Leven as establishing that fine race as a species — Salmo 

 ccecifer, and Dr Gunther distinguished it as S. levenensis; but their conclusion 

 has been vitiated by the fact that the number of caeca in Loch Leven trout 

 have been found to vary between forty -eight and ninety, and in trout from 

 other Scottish waters between twenty-seven and sixty-nine. This variation 

 is probably the result of diet, as the function of these appendages is sup- 

 posed to be that of a supplementary pancreas. Where food is plentiful and 

 rich, pyloric caeca will be found numerous, and correspondingly few when 

 it is scarce and poor. 



Again, the spinal column might be supposed to be of a less variable 

 character than organs composed of tissue; but even in this Dr Day found 

 the number of vertebrae in British trout to vary from fifty -six to sixty.* 



As to external character, every angler is familiar with the difference in 



colour and shape exhibited by trout inhabiting different waters, or even 



different parts of the same water. In this connexion I may be permitted to 



quote what I have described elsewhere as coming under my own observation: 



*'I possess a small lake, some five acres in extent, of exceedingly 



clear water supplied by springs. It has been formed out of an old 



marl pit, and about thirty [now nearly forty] years ago I introduced 



trout into it. The water being very rich in insect and crustacean 



life, the fish have thriven amazingly; but, owing to the absence of 



suitable running water, they are unable to fertilize the spawn which 



'Britiih and Irish Salmomda, p. 189. 



104 



