202 SALMONID^ OP BRITAIN. 



Limnea, and tubes of the Ephemeridae and Phryganeidse, while there was a fair 

 amount of fat around the pylorics. The upper and lower edges of the caudal fin 

 were also generally of a red or orange colour.* 



The adipose or dead fin in fishes living in clear streams, or where numerous 

 red spots are present on the body, is found to have as a rule an orange or 

 vermilion outer edge : or in some cases it has one, two or even three vermilion 

 spots on it. In some trout this red colour is wanting, while generally this fin has 

 a black spot but may have several. I have already alluded to the presence of this 

 red edging in the young fish (see p. 1 72 ante). I examined over 200 taken from the 

 river Loanan, in Sutherlandshire, and orange was present on this fin from the 

 very smallest. Those in peaty water are black, some possessing orange spots on 

 the adipose fin, whereas in others it is orange edged. It would seem that this 

 orange edging in some localities does not show itself until the second year of the 

 life of the fish. 



What causes the number, size, or form of the spots, cannot with accuracy 

 be determined. On April 4th, 1885, 1 was shown by Mr. Andrews, at Guildford, a 

 number of yearling trout reared from eggs obtained from the Wey : some had 

 brilliant but clear vermilion spots on the rayed dorsal fin, some had none, while 

 some had a few black spots on the body, but in others they were numerous as well 

 as on the fins. There were examples having the body densely covered with black 

 spots, others had none before the dorsal fin, while in some there were only a few 

 spots on the body and those of a small size. 



The cause of large black spots is difficult to account for, as in some peaty 

 streams where the fish are dark, some have few and very large spots, whereas in 

 others they are of about similar number but smaller. Some captured in deep 

 holes evidently have them of the first description.f In the example figured from 

 Moneyhouse burn near Howietoun, the fish which were captured by Mr. 

 Thompson were as follows, but in some finger marks were more clearly defined : 

 red along each margin of the caudal fin with a very narrow white outer edge ; 

 adipose dorsal with an orange edge round it. Pectoral with a very narrow red 

 and white edged upper margin : and with a reddish white edge. Eight finger 

 marks along the sides much wider than the ground colour. Eight red spots along 

 the lateral-line. Dorsal fin with a pinkish white edge. Ventral straw-coloured, 

 its outer edge white, stained with pink. A purplish hue over the body. The large 

 black spots have a light ring surrounding them. 



Varieties. — Trout, as already remarked, are exceedingly liable to variations of 

 form due to several causes. Some of these would seem to be hereditary; in 

 others the same exciting cause continuing in action occasions results as in 

 previous generations. These will be discussed under the heads of hybridism and 

 malformations. 



The observations of fish-culturists and field naturalists, respecting the varieties 

 of trout and the modifications to which they are susceptible, have already and 

 may still further prove most valuable in unravelling the confusion which has been 

 imported into this genus. 



Giraldus Cambrensis, lib. iii, c. x, the traveller and Archdeacon of Brecon, 



* December 4tli, 1884, examined the aquaria at " the Healtheries " and found that a most 

 interesting alteration of colour had taken place in some Lochleven and brook trout, also in a 

 large male S. fontinalis. The upper and lower edges of the caudal fin were white in all, and in 

 the fontinalis this was margined internally with red. As all these forms were similarly, although 

 unequally afEected, such must have been induced by some cormnon cause. In a neighbouring 

 tank were the remains of the Canadian trout, Salmo purpv/ratm, about twelve in number, all with 

 ragged tails and stunted growth, which was possibly partly due to the amount of Kme employed 

 for softening the water. It may be that this same agency had occasioned this whitening of the 

 caudal rays. 



t In the Itchen at Alresford, the keeper recognized two main varieties of marking in the 

 trout, the first with larger spots on the head and giUs, a shorter body and redder flesh when 

 cooked, these were said to mainly live on Crustacea and did not care for minnows. Secondly, 

 those close to Alresford where Crustacea are not numerous, but they devour large numbers of 

 minnows. 



