88 FISH AND FISHING IN SCOTLAND. 



small red worm. The average length of these parr was five and 

 a-half inches ; the smallest three inches. The roe in all, without 

 any exception, was at its minimum. 



Of the other ten males, caught on the same day, in the same 

 place, some had the milt large and vascular, but not so much so 

 as I have seen in July and August. 



In four of these ten the milt was at its minimum, having 

 undergone no changes. 



For the establishment and identification of distinct species, it 

 may freely be admitted, that the anatomical method is at once 

 the safest and the best ; and, when combined with the external 

 characters of the grown individual, leaves nothing to be desired. 

 But the case is somewhat different, and the method less valuable 

 in a practical sense, when applied to the young, and still more so 

 to the hybrid, which I consider the parr to be. 



The dentition, for example, seems to be the same in the parr, 

 smolt, and trout. I use the word seems, for I am not aware of 

 any minute anatomical inquiries having been made on this point 

 by others, and I cannot find, amongst the mass of notes before 

 me, the memoranda made at various times by my brother and 

 myself. The teeth of the salmonidse, as well as of most fishes, 

 are of uniform character, and present no such distinctions as 

 molar, incisor, and canine, by which we are enabled so clearly 

 and easily to note the various species of mammals. But they 

 are carried on a greater number of bones, and from this specific 

 characters may be deduced. In the having maxillary, intermax- 

 illary, mandibular, palatine, and vomerine teeth, all the salmonidse 

 agree ; but they differ when adult in respect of the number and 

 arrangement of the vomerine. 



In the common trout, the vomerine teeth are abundant (20) 

 are arranged in two interrupted rows, with the points turned 

 outwards, neither being precisely mesial. Many of the finest 

 of this species of trout have no transverse vomerine teeth, or, at 

 least, no row entitled to that name ; but others have : in certain 

 sea trout, at least, the vomerine system of teeth consists in 

 a few apparently mesial teeth, arranged in a single row, and a 

 transverse row on the chevron, whilst in the true salmon the 

 mesial teeth are still fewer, or absent, and the transverse row 

 still more distinct. 



