FRESII-WATEJi TROUT— C^CA AND VERTEBRAE OP. 189 



dissecting a i-ainbow trout, Salnw iruhus, at Ilowietoun, in March, 1887, which 

 had been liatchcd and I'oarcd in that establishiuciit, instead of 41 of these 

 appendages which it is said to possess in its native liill streams, it had 71. 

 And it is common for some continental varieties living in largo lakes to have 

 these appendages angmented in number. 



Again from some cause, as will liave to be again referred to when discussing 

 the Lochleven trout, when i"emoved to localities whei'c they delei'iorate, tliu 

 number of these appendages may become reduced. 



Instances of vai'iation in the number of these appendages are as frequent as 

 variations in the external colours of the fish, probably even more so, for local 

 causes occasion forms to have some colour characteristic of the locality, whereas 

 in the number of ca3ca no such constancy prevails. In the foregoing instances it 

 may be roughly stated* that, excluding the Lochleven race of trout, the number of 

 appendages obsei-ved to the south of the Bi'itish Isles has been found from 33 

 to 51, and in Scotland from 27 to G9. "While the southern form in New Zealand 

 has developed from 33 to 61. As to the Lochlevens they have been recorded 

 between 48 and 90 : the only constancy in short to bo found in these organs 

 consists in their inconstancy, but taking a wide expanse of rivers and waters for 

 examination, they are as a general rule more in number to the north in the 

 British Isles than to the south, similar in fact to what obtains in the races of 

 sea trout. 



It has seemed to me that at the commencement of the angling season I have 

 found in some waters where trout subsist largely on water snails, Lininea, that the 

 coats of the stomach are thicker at these periods than they are after the May fly 

 season when they have a more varied diet and do not appear to restrict themselves 

 so much to these snails. 



Vertebra}, respecting the number present in fresh-water trout, I have found 

 from 57 to 59 in Sutherlandshire, from 57 to 60 from the Windrush in Glouces- 

 tershire, 57 to 59 from the Churn on the Cotteswold Hills and 56 to 57 in the 

 Tivi. Mr. G. Sim, A.l.s., examined fourteen examples from Aberdeenshii^e : in 

 five males he found 68, 58, 58, 58, 59 ; in three from Kincardineshire, 59, 59, 59. 

 In six females from Aberdeenshire 58, 58, 58, 59, 59, 60, showing a variation in 

 numbers from 58 to 60. 



Dr. Giinther found in the northern form from 59 to 60, and the southern form 

 57 to 58; out of the fourteen examples in the British Museum collection there is 

 one from the Lyne with 59, one from the Isle of Man with 58, one from Northum- 

 berland 60, three from Cumberland 58, 58, 59, two from Shroj^shire 58 and 60, 

 two from the Usk 58, 58, one fi-om the Rhymney 58, one from Buckinghamshire 

 58, and two from Hampshire 57, 57. 



The foregoing figures would seem to demonstrate that the number of vertebra) 

 in the fresh-water trout, irrespective of whether it is taken to the north or south 

 of the British Isles, varies between 56 and 60. 



It is very evident that there is as close a relationshijD between the anadromous 

 marine trout and the non-migratory fresh- water forms as between the anadromous 

 and the land-locked salmon. Thus the anadromous sewin or sea trout of 

 Welsh rivers crosses with brook trout, and fertile oflspring are the result (see 

 p. 144a«^e). So also does the so-termed Galway sea trout, S. estuarins ov gaUivensis: 

 while the phinoc or whitling (p. 160 ante) passes by similar gradations into the 

 brook trout, or as observed by Sir H.Davy in Sahno7iia, p. 70, " The river and sea 

 trout seem capable of changing permanently their places of residence." 



I will now pass on to enumerate the various forms of fresh- water trout existing 

 in the British Isles, and which have been termed species. In thus separating 

 them such is done merely for the sake of easy reference to the writings of 

 authors, but not with any idea that most of them even deserve to be classed as 

 distinct races. 



* Doubtless increased investigations will show far more variations in number than given 

 above. 



