274 THE RIVER-SIDE NATURALIST. 



fine tortoise-shell. To what purpose, in the economy of 

 this fish, is this huge fin, so different to all the other 

 members of the salmon family, applied ? We have had the 

 opportunity of being able to watch large grayling when 

 completely at rest in a deep pool on the river Test, where 

 they were living in the greatest amity with a number of 

 large trout. As long as the grayling were quite stationary, 

 the great dorsal fin was lying folded over on one side of the 

 back, generally, if not always, on the left. When the fish 

 desired to rise to the surface of the water the fin was very 

 slightly moved, but when about to descend again it was 

 raised to its full extent, and it appeared as if its purpose 

 was to enable the fish to descend with great rapidity. 

 The fin probably on being raised acts on the muscular 

 fibres connected with the air-bladder, rapidly compressing 

 it, and thus increasing the quick descent so peculiar in 

 this fish. 



All who have watched a grayling after being hooked 

 will observe with what tenacity he endeavours to get to 

 the bottom, and how rigid and upright the dorsal fin con- 

 tinues during the fight. 



THE CHAR. 



The sub-generic group, Salvelini, contains the CHAR or 

 CHARR (Salmo alpinus). This fish inhabits the deep lakes 

 of Westmoreland, Cumberland, and Lancashire, some of the 

 lakes in Wales, and many of the lakes in Scotland. 



The British char has been divided by some writers 

 into six species ; Day considers there is only one, with 

 five varieties. The principal feature in this sub-genus 

 is, that there are no teeth down the body of the vomer, 

 but only on the head of that bone. The different species 

 are distinguished by colour, development of the maxilla, 

 size of the teeth, difference in the fin-rays of the dorsal 

 fin, caecal appendages, the size of the scales, and number of 

 the vertebrae. 



