8S PHYSOSTOML 



8- altois, Fleming, and the individual specimen the base of Parnell's figure, 

 plate xxxii, fig. 3, is in the British Museum collection as one of the types 

 of S. brachjpoma, Gtinther. It is evident that only the local east coast of 

 Scotland races formed the basis of his paper. 



Yarrell's S. eriox and S. trutta, as seen by his collection now in the British 

 Museum, included the sewin or S. cambricus, also the S. albus. Two were 

 8. trutta, about twenty S. cambricus besides many small ones, and one 8. albus 

 forming one of the types of S. bracliypoma, Gtinther. 



Thompson observes that his S. trutta is identical with S. albus, the Scotch 

 Herling sent him by Captain Fayrer, and that he found a perfect agreement 

 between them, while his S. eriox he asserted to be 8. cambricus or the sewin. 



Couch largely augmented the nominal species of salmonida? and gave the five 

 following : SaJmo trutta which he terms Peal, and observes that under several 

 names it is known in considerable abundance through the whole extent of the 

 British Island, 8. cambricus or sewin, Sea-trout from the Fowey in Cornwall, 

 evidently identical with the so-called hybrids of the sewin. 8. trutta no. 2, 

 termed salmon-trout, which he asserts to be more a fish of the north than 

 the generality of this genus, and seems to be identical with S. eriox, Yarrell, 

 or a compound of 8. albus and S. cambricus. This author appears to have 

 been misled by two circumstances ; first, he accepted without due investiga- 

 tion the numerous subdivisions into which he found this species being divided 

 by those who held every little difference to be diagnostic of a distinct form 

 or the result of hybridization, and any who questioned such were deemed 

 incompetent observers suffering from confused ideas.* As a result he seems on 

 finding: what he conceived to be some fresh but slight modification to have 

 supposed he had discovered another new species, thus adding to the contusion 

 already existing. In fact (at p. 204) he remarks upon the difficulty of assigning 

 to his specimens the names given by the writers on the continent, and supposed as 

 a reason " that there exists several kinds of the Sahnonidce which are not yet clearly 

 defined," and that not a few of the known varieties will be discovered to be 

 distinct species. Secondly, it would seem that his descriptions were, at least in 

 several instances, made from his drawings, which, if artistic, are scarcely accurate. 



Widegren (OfV. Vet. Akad. Fork. 1863) gave an interesting paper in which 

 he asserted that the anadromous sea-trout and non-migratory fresh water forms 

 were all variations of one species, the differences being due to the localities they 

 inhabited. Sterile forms, or rather those suffering from temporary sterility, 

 having the caudal fin generally (but not invariably) more forked, and their 

 colours more silvery than is seen in such as are in a breeding condition. In these 

 conclusions Malmgren generally agreed, and they appear to coincide with the 

 results of the experiment I have alluded, to and the series of examples in our 

 national collection. 



B. x-xii, D. 12-14 (J^)/0, P. 13-14, V. 9, A. 11-13 (|:f), C. 18-19, L 1. 

 115-130, L t. |f:||, Vert. 59-00, Coec. pyl. 33-61. 



Body rather elongated, and the abdominal profile more curved than that of 

 the back. The proportions of one part of the body to the remainder, more 

 especially the length of the head, vary considerably in this species, and though 

 1 consider the fresh water brook-trout specifically the same, the following 

 measurements and remarks solely refer to the anadromous form, unless otherwise 

 stated. The young in most respects are similar to the young of the salmon, while 

 in the adult fish the head in the male is generally longer than in the female. 

 Length of head 4| to 5|, of caudal fin from 7j to 8, height of body from 4 to 5 

 in the total length. Eye diameter about 7 to 7\ in examples exceeding 15 inches 

 in length, about 2 to 2|'diameters from the end of the snout, and the same distance 

 apart : it is comparatively larger in the young. Interorbital space convex, and 



* Fit/.inger when asserting Salmo Schiffermnelleri, Bloch, to be a hybrid (Sitz. Ak. Wien, lxxii, 

 1876, p. 255) seemed to lave been mainly guided in liis decision by ascertaining that the reproduc- 

 tive organs only exist in a rudimentary condition in the joung" si age, degenerating into adipose 

 tissue in the adult. 



