bo THE SEA-TROUT 



I may now state more precisely wherein the teeth of trout differ 

 from those of sea-trout. There are always, I think, two rows of teeth 

 on the vomer in the case of both fish in their earlier stages of growth, but 

 as the fish get older the teeth are more or less freely shed and they 

 disappear the more rapidly as the fish adapts itself to a salt-water 

 environment. As to this matter Dr. Day, I think, writes with consider- 

 able weight of authority. " However," he states, " the dentition varies 

 excessively, while we find examples possessing the colours, form, etc., 

 of the brook trout resident in brackish waters or even the sea, but mostly, 

 not invariably, possessing the limited number of vomerine teeth of the 

 anadromous forms. On the other hand there are anadromous forms 

 (in colour) in fresh water, with the teeth assuming that present in the 

 brook trout or retaining the par dentition. It has been asserted and 

 reasserted that brook trout invariably have a double row of teeth along 

 the body of the vomer, and some authors have gone so far as to insist 

 that these teeth are not deciduous. Doubtless it is not uncommon to 

 find trout, even up to 2 lb. weight or even more, with all the vomerine 

 teeth thus remaining intact when a double row is present, but it is by no 

 means rare to see only one irregularly placed row. While in very large 

 specimens these teeth (unless they have entirely disappeared) are always 

 in a single row, and the vomer may be found even toothless or with one 

 or two teeth at the hind edge of the head of that bone. Equally 

 incorrect is the statement that the teeth disappear differently in different 

 forms, for in all they first assume a single row and then fall out, first 

 commencing from behind. But in the rapidly growing sea-trout the 

 vomerine teeth are shed sooner than in the brook trout." In illustration 

 of this passage from Dr. Day's work the reader may refer to the drawing 

 which I give of the vomer of a trout weighing 13 oz., taken from above 

 the Falls of Clyde (Fig. 17). The spaces which the shed teeth occupied 

 arc distinctly seen, and the double row of teeth is clearly in process of 

 becoming a single row. The diagram (Fig. 18) shows the dentition of 

 a sea-trout of 2^ lb. 



