5 oo TUBE-BLADDERED GROUP. 



river-trout may be taken the Lochleven trout, which is somewhat silvery during 

 the smolt-stage, with the spots generally black, and no orange border to the fatty 

 fin, but at a later stage assumes the general coloration of the river-trout, although 

 lacking the white black-based front margin to the dorsal, anal, and pelvic fins 

 characteristic of the latter. Silvery trout do, however, occasionally occur in fresh 

 waters, where there is no possibility of their having migrated from the sea. In 

 concluding his observations concerning the coloration of trout, Day writes that 

 " reasons have been shown for admitting that sea-trout might breed in fresh waters 

 without descending to the sea. That they can be traced step by step, and link by 

 link, into the brook-trout, and vice-versd ; that the Lochleven trout, which normally 

 possesses a smolt- or grilse - stage, passes into the brook-trout ; and also that 

 breeding any of these two forms together sets up no unusual phenomena." Later 

 on, he observes that some of the chief distinctions between the sea- and fresh-water 

 forms of trout consist in the comparatively more complete system of dentition in 

 the fresh-water races, their generally longer head, blunter muzzle, and stronger 

 upper-jaw, irrespective of the smaller number of blind appendages to the intestine. 

 The dentition is, however, excessively variable ; and specimens with the coloration 

 and form of the river-trout taken in estuaries, or even in the sea, usually have the 

 small number of vomerine, teeth characteristic of the migratory forms ; while, on 

 the other hand, fresh-water examples with the coloration of the migratory type, 

 may have a dentition of the nonmigratory type. " It has been asserted 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 assert that these teeth are not deciduous. 

 Doubtless it is not uncommon to find trout up to 2 lbs. 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 toothless, or with only one or two teeth 

 at the hinder edge of the head. 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." The limits 

 of our space preclude our entering further into the consideration of this interesting 

 subject. The ordinary sea-trout, which is essentially a North-European fish, much 

 more common in Scotland than in England, and grows to a length of 3 feet, is 

 depicted in the lower figure of the illustration on p. 493 ; while, as an example of 

 a spotted form, we take a variety of the Continental lake-trout (S. lacustris), 

 shown in the upper figure of the illustration on p. 499. Known on the Continent 

 as the maiforelle (May-trout), this fish has the sides of the body marked with 

 irregular angular or X-shaped black spots, between which are red spots, these 

 spots becoming less numerous beneath the lateral line, while the under surface 

 may be tinged with red. On the gill-cover the spots are larger and more rounded. 

 In the typical variety of this trout, from the Lake of Constance, the spots do not 

 extend below the lateral line ; this form being known as the schwebforelle. The 

 migrations of the sea-trout are very similar to those of the salmon : in Sutherland 

 the great run of these fish to the sea taking place in June, while they reascencl 



