FRESH-WATER TROUT— LOCHLEVENS DESCRIBED. 221 



Fig. 49. Maxilla of female trout. 1, specimen from Otago, 19'2 in. 

 long. 2, specimen of Lochleven trout from Howietoun, 20 in. long. 



trout, as, for instance, those in Sutherlandshire, tkis difference is not so striking. 

 It will similarly be seen to be the case on comparing the jaw of a large female 

 brook trout with that of a Lochleven. But it is evident that in Lochlevens 

 reared at Howietoun, the males have not such strong jaws or teeth as those living 

 in a wild condition, which is probably owing to their having from their earliest 

 existence had food provided for them. Also as regards trout, very probably age 

 should also be taken into consideration as well as size, for a large four-year-old 

 Howietoun male would probably be less strongly armed than a similarly sized fish 

 which had been reared in a loch or stream, and which had most likely taken a 

 greater number of years to attain to the same size. Likewise, when examining 

 this subject, care must be taken that the accessory bone of the maxilla does not 

 by its position make it appear in a figure that the jaw was exceedingly strong, for 

 this in reality has but little to do with strength, in fact it has been considered 

 as probably homologous to an ossified labial cartilage. As to the male having 

 no knob on the lower jaw, that likewise is a most erroneous assertion ; in the one 

 figured in Plate VI, fig. 1, and which fish measured 14'6 inches in length, and was 

 44 months of age when caught in October, 1886, the knob was very well developed. 

 This knob is constantly seen in all old males of this form ; while even in some old 

 females at Howietoun a small one has occasionally been observed. 



As to the maxillary bone being " much narrower and more feeble than in 

 8. fario, in specimens 13 inches long it extends to below the hinder margin of the 

 orbit, and at no age does it reach beyond it "* (CHinther). This statement as to 

 where the maxillary bone extends posteriorly, and first made by Dr. Giinther, is 

 not borne out by an inspection of Howietoun fish or those from Lochleven, in 

 which in large specimens it extends from one to two diameters of the orbit 

 posterior to the eye, and this is of normal occurrence. In a Howietoun example 

 26 inches long, it reaches to 1| diameters of the orbit behind the eye ; while a total 

 length of 27 inches is that of the longest fish which has been captured in that 

 establishment. For as they become more or less sterile at from 8 to 10 years of 

 age, a time to which breeding males rarely attain, they are no longer profitable, 

 and therefore older fishes are not kept. 



The male figured (Plate VI, fig. 1) was 14-6 inches long, and captured at 

 Howietoun, September, 1886 ; it was 3^ years old, length of head 4Jt in that of 

 the entire length of the fish. Maxilla rather narrow and extending to behind the 

 hind edge of the orbit, consequently in this specimen it must have grown rapidly, 

 raising the question of whether it would not have become thicker with age. 



the features of a salmon and the sea trout. . . . The fact of one of these trout having, in the 

 course of the present trial, been regarded by Professor Young as a sea trout, after examination, is 

 a very strong testimony to the difference between the characteristic features of the Lochleven 

 trout and those of all the non-migratory river-fish " (pp. 166, 167). 



* The teeth in the maxilla of S. levenensis, in Dr. Giinther's figure, are shown as directed 

 forwards and upwards, the base of each tooth appears as if resting on the skin with its point 

 turned towards the maxillary bone ! {See page 146 ante.) 



f In a female from Lochleven 14-4 inches in length captured about the same time, the head 

 was 5J in that of the entire length of the fish. 



