THE COMMON BROWN TROUT. 219 



the disintegration and digestion of the shell fish on which this trout seems 

 to feed most usually. But this organ can hardly possess a grinding power, 

 because of its interior surface being lined with a fine yellow coat, which is 

 by no means fitted for mastication. The ordinary trout differs in this 

 feature so much that its stomach coats are not so thick by two-thirds. 

 Professor Owen has examined the fish, and thus speaks of it (Lectures 1, 

 234) : " It is the ascending or pyloric half of the heart or sipteral stomach 

 that has its muscular parietes unusually thickened, by which it is enabled 

 to bruise the shell of the small fiuviatile testaceans that abound in the 

 streams to which this species of trout is peculiar." 



Ordinarily such a marked difference in the anatomy might entitle the 

 fish to claim itself as a different species ; but my idea is, that a slight 

 structural change through successive generations, originated by an 

 accident of food, has been gradually built up and confirmed till the 

 structure of the fish has become as we find it now. Yarrell gives the 

 fin rays of the gillaroo trout as follow : Dorsal 12, pectoral 12, ventral 

 9, anal 11, caudal 19, vertebrae 56. It may be added that Pennant looked 

 upon this fish as only a variety. It is found chiefly in Ireland, but Couch 

 says it has been taken in Sutherland and at Wick. 



The colours and general appearance of this trout are thus described : 

 Depth of specimen in front of dorsal fin, 2 Jin., rising higher at the back 

 and deeper at the belly than the kindred species, compared with which 

 the under jaw is shorter and much more feeble, the snout more obtusely 

 rounded, the setting on of the pectoral fins thrust more forward under the 

 plate which borders the gills, and which is turned up to give them place ; 

 the pectoral and ventrals also proportionably larger, the anal rather 

 smaller, the tail less expansive. The ordinary colouring is as follows : On 

 the head brown, bluish brown along the back, higher portion of the sides 

 tinted with pink, verging into yellow, and on the belly white ; cheeks 

 yellow ; pectoral and anal fins yellow, also dorsal, dusky, with black spots 

 and pale anterior border, adipose fin dark with black spot. Vermilion 

 spots are scattered over the sides of the fish, with no reference to the 

 lateral line, or very little. The flesh is a rich salmon colour. 



Before passing from the general history of the fish, perhaps I may be 

 allowed to quote from that curious poem, Mickle's " Syr Martyn," in 

 reference to the metamorphosis of the trout : 



For once she lived a nymph of spotless fame 

 In an obscure retreat, and Truta was her name. 

 It chanc'd that in a flow'ry path she stray" d, 

 Where a clear river with the pebble play'd, 

 And just disturbed the silence of the shade. 

 Truta, now seated near the spreadingltrees, 

 Enjoys the coolness of the passing breeze ; 

 In the clear stream she casts her modest eyes, 

 And in a fillet her fair tresses lies. 



