Sketches of Irish Natural History. 549 



Dr. Giinther has often founded a new species, rather as it seems on the 

 locality where taken than upon any permanent and invariable specific 

 characters, what are we to do, who, while wishing to know our native 

 fishes, find ourselves quite unable to determine the various forms? 

 These come so near to one another, that it is often nearly impossible to 

 separate them, and, after some hours of careful study, we find ourselves 

 still full of doubt and perplexity while trying to follow our recognised 

 best authority ; yet, unable to feel certain that we have identified our 

 species correctly. What are we to do when we find one excellent 

 authority, Sir W. Jardine, describing as distinct a large trout from 

 deep-water, which another equally skilled authority tells us is only a 

 large, overgrown monster, which, like Orestes, has taken to devouring 

 his own, and his neighbour's progeny ? A third excellent authority 

 considers a thickly-coated stomach a sufficient character to establish a 

 new species "the Gillaroo." 



Another good anatomist, when he captured the brown trout in 

 brackish water, where the fresh meets the salt water, called it 

 S. estuarius. 



Fortunately, it is chiefly among the salmonidce, or trout family, that 

 these nice and subtle distinctions have been tried. Practical fishermen 

 complain that they cannot follow them or understand them ; and, when 

 it is once appreciated, how infinitely variable are trout in appearance 

 and character, we may almost say that every lake, or pool, or river, has 

 its own distinct form. The real difficulty is not in seeing and recog- 

 nising differences, so much as in knowing how to make a philosophical 

 combination of many forms under one name. 



Among botanists, the recent over- refinement of distinctive characters 

 has led to many mistakes in identification, and to making many a pro- 

 mising botanist give up his studies, in view of the enormous difficulties 

 which have been raised in distinguishing the veiy slightest variation of 

 brambles, hawkweeds, roses, water-crowfoots, &c. Indeed, many 

 naturalists are content to omit altogether the study of these perplexing 

 forms. 



In Ireland we have at present two forms of charr. One, S. colei, 

 occurs in Lake Coomhasarn, &c., in Kerry; the other in Lough 

 Melvin. 



No doubt many other forms exist in unexplored lakes, and will 

 remain to perplex the future ichthyologist. A migratory trout has been 

 described as Salmo gallivensis ; but how extremely improbable is it 

 that this is not a form of one or other of our well-known sea-trout. 

 Another sea-trout at present imprisoned in Lough Leven (Scotland), 

 and apparently cut off from all access to the sea, has received a specific 

 name as Salmo levenensis. That is, a sea-trout has become altogether 

 changed by a long residence in fresh water, somewhat as the estuary 

 trout (of Knox) has received its name from having been captured in 

 brackish water. Similarly, there is a small race of the Twaite Shad 

 (Clupea finta), which is taken in the Killarney lakes, and has appa- 

 rently given up its usual migration from salt to fresh water in the 



