220 



SALMONID^ OP BRITAIN. 



in the brook trout. Although certainly this is sometimes the case, such characters 

 are not persistent. 



In measuring a number of Howietoun examples, I find that in specimens from 

 3 to 4 inches in length, the head is from 4f to 5 in that of the entire length. In 

 males, from 7 to 10 inches in length, it is from 4^ to 4|, and in examples from 14 

 to 15 inches, it is from 4 to 4|in the same length. In females from 8 to 10 inches, 

 the head is 4| to 5 in the entire length, from 13 to 14 inches, about 5| in the 

 same distance, and at 20 inches one-fifth. 



In form of the body there is no difference perceptible in those fishes reared in 

 Gloucestershire or at Guildford, from eggs obtained from Howietoun, and young 

 of brook trout raised from local brook trout eggs. It is thus seen that this 

 ultimately depends upon local circumstances or conditions ; for if they are removed 

 to another locality where these conditions are different, they assume the local 

 brook trout form. The same observation applies to the length of the head, which 

 in some well-fed examples, and, in fact, generally so in the young raised at Howie- 

 toun, is a little shorter in proportion to the length of the body than is usually 

 seen in the brook trout, but this likewise alters on their being transferred to a 

 new home. 



lEyes. — Diameter in an 

 example about f lb. weight, 

 51 in the length of the 

 head, 1^ diameters from 

 the end of the snout, and 

 the same distance apart : 

 it is of greater comparative 

 size in small specimens, 

 but smaller in larger ones. 

 Interorbital space convex. 

 The lower limb of the 

 preopercle is rather short, 

 as will be seen in the 

 examples shown in figure 

 48, and on comparing 

 them with examples from 

 Loch Assynt, in Suther- 

 landshire, the differences 

 were very slight, but in 



Fig. 48. Preopercle of Looh- 

 leven trout. 1, female, 10-9 in. 

 long : 2, male, 14 in. long : 3, 

 female, 19-2 in. long: 4:, female, 

 20 in. long : 5, female, 23 in. long. 



some specimens from the 

 south of En gland, the lower 

 limb of this bone was 

 longer. Maxilla rather 

 feeble, it reaches to slightly 

 behind the hind edge of 

 the eye : lower jaw with a 

 hook or knob at the upper 

 end of its extremity. It 

 has been said that the 

 maxillse of the Lochleven 

 trout are weaker than 

 seen in the brook trout, 

 and this is correct to a 

 great extent if we com- 

 pare forms from the South 

 with undoubted Loch- 

 levens. But if the com- 

 parison is made with loch 



spring" (p. 37). In tlie Journal of the Unnean Society (Deo. 19tli, 1854), Dr. Knox remarked, 

 that at first he thought this a specffie form, "although anatomical investigations had not hitherto 

 confirmed it." 



Dr. Giinther, I. c, gave a fuller description than the previous authors whom I have quoted. 

 He observed of this fish that it has the " body much less stout than in S. fario. ... In the male 

 sex a mandibular hook has never been observed. Maxillary much longer than the snout, but 

 much narrower and more feeble than in S. fario (see figures, p. 6) ; in specimens 13 inches long, 



it extends to below the hinder margin of the orbit, and at no age does it reach beyond it 



The teeth on the body of the vomer form a single series and are persistent throughout life. Pins 

 well developed, not rounded." He found from 49 to 90 oajcal appendages, while at p. 6 are 

 figured two maxillary bones, stated to be from 8. fario and S. levenensis ; but not being completed 

 at their proximal extremities renders it almost impossible to understand for what they are 

 intended to represent. The supplementary bone would seem to be where the most difierence 

 exists. 



In giving a decision on the well-known " Orange-fin " case, in 1872, the Sheriff Substitute 

 found " in reference to the outward silvery appearance of the fish in question, both Dr. Giinther 

 and Professor Young state that the silvery coat with which these fishes are clothed is to be regarded 

 aa a distinctive mark of their being migratory fish of the salmon kind. The assumption of the 

 silvery coat .... in the case of river fish, is to be held an almost infallible test of a migratory 

 and sea^going habit. Nor is this inconsistent with the well-known fact, that in the case of certain 

 fish which inhabit lochs having now no communication with the sea, a similar silvery appearance 

 is to be seen. In the case of the Lochleven trout, which affords the most notable example of 

 the phenomenon referred to, it must, however, be kept in view, as having an important bearing 

 on the character of this fish, that the loch which it inhabits had, most probably, at one time a 

 communication with the sea, and that the fish themselves possess in a most remarkable degree 



