188 SALMONIDiE OF BRITAIN. 



Dr. Giinther observed in the yellow-fin case, 1872 (p. 127), another important 

 matter is the form of the caudal fins. " In Salmo fario, which requires a special 

 kind of caudal fin for locomotion in running water, it is different from the same 

 fin in ;S'. fruffa, which are fish which go do\vn to the sea to comparatively still 

 water. Those fish living in the river require a much stronger caudal fin, and 

 you find that in Salmo fario the caudal fin is wholly of strong rays and the lobes 

 become more obtuse and rounded, and it is in fact a short paddle." If the reader 

 will compare the outlines of caudal fins in S. trutta (p. 156 ante\ sewin (p. 163 

 ante), and the brook trout (p. 199), he will probably see reasons for doubting 

 the soundness of these statements. 



Ca'cal appendages. — So many erroneous statements and still more erroneous 

 deductions have been made respecting the number of ca3cal appendages present 

 in the fresh-water trout, that it becomes necessary to enter upon the subject a 

 little in detail.* Among those personally examined and respecting which notes 

 have been kept, many from Suthei^landshii^e had from 46 to 50 ; one from 

 Yorkshire 35 ; from the stream at Colesbourne in Gloucestershire 34, 34, 38, 38, 

 39 ; from the Windrush 39, 42, 45, 45, 49 ; in six from Cardiganshire from 35 

 to 44. Dr. Hamilton found in two examples in Inverness-shire, 27 and 40. 

 Pamell never found upwards of 49 in Scotland. 



As regards Lochleven trout, Richardson found 73, Parnell 80, and Giinther 

 from 49 to 90, while at Howietoun 1 have found them vary form 48 to 82 in 

 the male fish and between 45 and 66 in the female, as will be subsequently given 

 more in detail. 



Among the examples of Salmo fario in the British Museum collection, the 

 number of the ceecal appendages have been recorded as follows : — one from the 

 Dee with 44 ; one from Northumberland, 44 ; two from Shropshire, 34, 34 ; many 

 from the Usk, 40 to 45 ; one from Buckinghamshire, 41 ; and seven from the 

 Wandle, 39, 41, 41, 42, 47, 49, 51 ; one from Hampshire, 47 ; and one from the 

 Erme, 44, 



Mr. G. Sim, a.l.s., of King Street, Aberdeen, has been good enough to 

 make the following obervations on the casca of fresh-water trout : he considers 

 that in such wild forms as have been fed luxuriously, these organs are always larger 

 and have thicker walls than ordinary, while underfed ones have them short and 

 with feeble coats. Most of the following were taken in lochs or streams where 

 no introduction of other forms has occurred. Males : eighteen from Aberdeen- 

 shire, 29, 33, 38, 38, 39, 41, 44, 46, 47, 48, 49, 49, 49, 54, 55, 55, 56, 69; seven 

 from Kincardineshire, 32, 36, 38, 39, 40, 40, 41. Females: twenty-three fi'om 

 Aberdeenshire, 30, 36, 37, 39, 39, 39, 43, 43, 43, 44, 44, 44, 44, 45, 47, 47, 47, 47, 

 48, 50, 51, 52, 59 ; sex not recorded, four from Aberdeenshire, 44, 45, 50, 61. 

 Males in Aberdeenshire showing an average of 50 cceca, in Kincardineshire of 38. 

 Females in Aberdeenshire 44, those of sex not recorded, 50 : thus giving 

 a variation between 30 and 69 and a general average of about 46 of these 

 appendages for the 52 examples. 



Passing on to the number found by the late Mr. Arthur to be present in our 

 brook trout raised in New Zealand, we find he recorded that from seven male 

 and twenty-seven female fish taken from nine different rivers, a lake, and the 

 Otago harbour, these appendages ranged from 37 to 55 in the males, with a mean 

 of 48*7, and from 33 to 61 in the females, with a mean of 47'3. 



It would appear from the foregoing figures that considerable variations are 

 perceptible among trout even when residing in the same locality and under the 

 same conditions. Whether deficiency or mal-assimilation of food is competent 

 to reduce the number or size of these organs, or rich living to increase them, are 

 qiiestions that cannot as yet be decided. But it is remai'kable that forms from 

 the south of England reared in Australasia under warmer conditions and possibly 

 more abundant food have developed from probably 38 to 48 up to 61. That this 

 may be due to this cause, a rather con-oborative case has occurred : for on 



* See the numbers of cix-ca attributed to each form of trout by different British authors 

 (p. 11 ante). 



