102 PHYSOSTOMI. 



I have already (p. 57) alluded to the parr marks of the young being 

 occasionally continued throughout life in small forms, evidently adding to the 

 confusion respecting what is a parr. 



Varieties. Trout, as already remarked, are exceedingly liable to variation, 

 due to several causes. Some of these abnormal productions would seem to be 

 hereditary ; in others the same exciting cause continuing in action occasions 

 results as in previous generations. Giraldus Cambrensis, lib. iii, c. x, the 

 Archdeacon of Brecon, who attended Baldwin, Archbishop of Canterbury, 

 in a progress through "Wales in 1188, tells us of eels, trout and perch existing 

 in the lakes of Snowdon which only possessed the right eye, but being 

 invariably blind with the left. The Fischau, near Mandorf in Germany, was 

 reputed to contain blind trout (Fr. Ern. Bruckmanni Epist. Itin. xxxvi, Wolfenb. 

 1734, p. 10). A deformed race of trout is asserted to exist in a small loch in 

 Invernesshire near Pitmain ; among them there appears to be an arrest of develop- 

 ment in the upper jaw, giving their heads a slight resemblance to those of bulldogs, 

 due to the projection of the lower jaw (Encyc. Brit. 7th ed., art. Ang.). Similar 

 malformations are seen in the "ground trout " of Penyghent (Yorkshire Vertebrata) 

 and many other places. In Loch Islay exists a race of tailless trout, Salmo 

 Islayensis, Thomson (Traquair, Journ. Anat. Phy. vi, p. 411, pi. xix, and 

 Thompson, Science Gossip, 1872, p. 85), which in some streams has been traced to 

 be due to the action of deleterious matter in the water (see Angler's Note Book, 

 1880, p. 66). Mr. J. Harvie-Brown observed, about 1876, in the river Carron that 

 a contraction of the rays of the tail fins of the trout commenced, due it was 

 universally believed to continuous pollution of the water through the agency of 

 paper mills. At Malham Tarn, in Yorkshire, 1240 feet above sea level, the trout 

 are distinguished by a deficiency or malformation of the gill-covers in about one 

 in every fifteen captured. As I have seen the same result from breeding in 

 confined places, I believe such to be one at least of the causes, perhaps conjoined 

 with gill-fever when young. On Plinlimmon, and in adjacent parts of Wales, are 

 " hunch-backed " trout, having deformed vertebral columns as already alluded to. 

 In some, at least, of these instances the young are reared where cascades are falling 

 over heights into a series of pools, and it has seemed to me not unlikely that 

 either the egg or the fry coming within the reach of such, might suffer injury, 

 and consequent disease of the spine (so common in fishes) be set up. Barrington 

 (Phil. Trans. 1767) remarking upon some examples crooked near the tail 

 continues, " these trout are only caught in a small basin, eight or nine feet deep, 

 which the river forms after a fall from the rocks." Perch were found to be 

 similarly affected, the same cause acting apparently on both forms. There are 

 likewise races in which some local cause has set up local action, as of the stomach 

 alone. This variety, the Gillaroo (see page 99), due to the food it indulges in, has 

 the muscular coat of its stomach thickened, which abnormal structure has been 

 reproduced in succeeding generations. For it must not be assumed, because in 

 certain examples we are unable to find Lirnnea and other shells, that the fish has 

 never consumed any ; they may have been digested, or it may have varied its food, 

 or the shells may have been temporarily unobtainable. In County Derry, in the 

 river Glenlark in the Munterloney Mountains, "Mr. Sinclaire states that the 

 water and stones are deeply tinged with a rust colour, of which the trout likewise 

 partake. Their flesh is very bad and of a metallic flavour ; so bad are they that 

 the country people will not eat them, and as they are not fished for, the river 

 abounds in them " (Thompson, iv, 153). 



Lunel remarking upon the various specific names that had been given to the 

 varieties of this species, asserted Salmo fario, 8. lemanus, S.rappii and 8. laciistris, 

 of Lake Constance to belong to one form which he proposed terming S. variabilis. 

 Steindachner (Ak. Wiss. Wien, lii, 1865, Nov. 30th) identified 8. detex, Heck, 

 with 8. fario. Pavesi (Pesci nel Ticino) considered the lake and river-trout of 

 the Canton to be merely varieties of one species. "Unquestionably," observes 

 Stoddart (Angler's Companion, 1847, p. 3), "there exists no species of fish 

 which, judging of it by the external marks, holds claim to so many varieties 

 as the common freshwater-trout. In Scotland almost every lake, river, and 



