146 SALMONID^ OF BRITAIN. 



breed in fresli waters without descending to the sea. That they can^ he traced* 

 step by step, and link by link, into the brook trout and vice versa : that the 

 Lochleven trout, which normally possesses a smolt or grilse stage, passes into the 

 brook trout; also that breeding any of these two forms together sets up no 

 unusual phenomena.f 



Our anadromous sea trout are able to take on a fresh- water state of existence, 

 and breed there ; irrespective of which by almost imperceptible degrees we find 

 them in eveiy country passing from one form into the other, which raises the 

 question of which form Sahno orcadensis, S. estuarms, &c. (described as new 

 species by Dr. Giinther), most resemble, the anadromous *S'. trutta or the fresh- 

 water S. fario. Believing the two latter to be merely the extreme limits of one 

 species, it becomes unnecessary to decide whether the diminution in the number 

 of the vomerine teeth is symptomatic of the fresh-water form developing towards 

 its larger relative the anadromous sea trout, or whether it is the sea ti^out retro- 

 grading towards its par dentition, or that which is often but by no means always 

 persistent in Salmo fario. Colours, it is true, are not very reliable, but these forms 

 more nearly approach the fresh water than the saline varieties, a change which 

 appears invariably to occur sooner or later in anadromous forms which become 

 permanent residents in fresh water. 



Some of the chief distinctions between the sea and fresh-water forms of trout, 

 consist in the comparatively more complete system of dentition in the fresh- water 

 races, their generally longer heads, blunter snouts, and stronger maxillae, irre- 

 spective of the decreased number of the coscal appendages. 



However, the dentition varies excessively, while we find examples possessing 

 the colours, form, &c., of the brook trout resident in brackish waters or even the 

 sea, but mostly, not invariably, possessing the limited number of vomerine teeth 

 of the anadromous forms. On the other hand there are anadromous forms (in 

 colour) in fresh water, with the teeth assuming that present in the brook trout 

 or retaining the par dentition. J {See p. 21 ayite.) It has been asserted and 

 re-asserted that brook trout invariably have a double row of teeth along the body of 

 the vomer, and some authors have gone so far as to insist that these teeth are not 

 deciduous. Doubtless it is not uncommon to find trout even up to 2 lb. weight or 

 even more with all the vomerine teeth thus remaining intact when a double row is 



* An experiment was made on Tweed. Sabnonidee as allutlecl to by Mr. Brotherston of Kelso, 

 who tells us that a Committee selected 133 examples of orange lins which they placed in Carham 

 pond in May, 1874. The Committee (with the exception of two) as well as practical fishermen, 

 who from time to time personally attended the examination of these fish, were convinced that 

 they had successively changed their character of orange fins for that of black-tails and %yhitling. 

 The two of the Committee who disagreed were Major Dickens and Mr. Stoddart, who maintained 

 that they were yellow trout. In May, 1879, some were liberated, having had a wire inserted into 

 the flesh behind the adipose fin with the stamp " Tweed iv." Two were captured June 4th and 5th, 

 near Birgham-on-the-Tweed, and came into Mr. Brotherston's hands, and he found they were 

 brook trout. One which had been put into the Tweed on May 21st, 1879, 12 in. long and 

 weighing 12 oz., was recaptured June 4ch, near Birgham-on-the-Tweed, and when recaptured 

 was 12.V in. long and weighed 10| oz. Mr. Brotherston asserted that it was a brook trout. A 

 second^was recaptured near the same place July 17th, it was 17-J in. long and weighed 28^ oz., 

 it also was sent to Mr. Brotherston, and was likewise a brook trout, as were some others. Both 

 parties stoutly maintained the idea that these young fish were sea trout or brook trout, and 

 it seems to me both were correct, for like the chameleon's colours they were referring to what 

 arc merely varieties of one species. 



f In November, 188G, Sir James Maitland, at Howietoun, laid down some eggs of the sea trout 

 in order to follow out their life-history if kept in fresh-water ponds ; 350 hatched in 1887. 



+ It is remarkable how erroneous statements in Ichthyology are continued _ by compilers 

 even after they have been disproved. Dr. Giinther, in 18G6, asserted that in the Loch- 

 leven trout the maxillary bone never reaches to behind the eye : that there is no knob at the end 

 of the lower jaw in males, and that the tail fin is never rounded, which are all merely errors of 

 description. In plate vi will be seen a young male with the knob in the lower jaw, the upper jaw 

 also extending beyond the vertical from the hind edge of the eye, while in the woodcut showing 

 the form of the caudal fin in this variety it will be apparent that it becomes as rounded with age 

 as in the other races. A most incorrect woodcut (in the British Museum C'atalo[iue, vol. vi, p. 6) 

 of the upper jaw as compared with that of the brook trout has been produced, which even shows 

 maxillary teeth looking upwards and inwarda, while the size of the bone, as delineated, does not 

 agree with what is normally present iu Lochleven trout. 



