36 I'CENDALL: NEW ENGLAND SALMONS. 



plainly saw him eject a sea-trout }/i lb. to ]4, lb. in weight, which we picked up,- scarred 

 a good deal and, of course, dead, but quite fresh. I was fishing with worm, and killed 

 a good many salmon with worm that month, but a very few with a fly. 



'My opinion always has been that salmon in fresh water though they of course get 

 poorer and more out of condition the longer they are away from the sea, feed sufficiently 

 to avoid starvation, but directly they are hooked eject everything in the stomach, 

 though there is usually difficulty in observing this.' 



As the exception that proves the rule that salmon do not feed in fresh water, Calder- 

 wood (1930, p. 73) cites the following instances, 'I have known four instances of fish in 

 rod-caught salmon in the last thirty years; a trout in a salmon caught in Loch Shiel, 

 a char in a salmon taken, if I remember rightly, in Loch Tay, a trout in a salmon caught 

 in the Thurso, and five parr taken in a salmon caught in a tributary of the Tweed.' 



But as Miescher-Rusch (1883, p. 462) remarked in connection with another subject 

 pertaining to the Rhine salmon, 'I feel compelled to warn people not to apply the 

 experiences gained in other rivers to the Rhine salmon, and vice versa.' The fact that 

 conditions in different rivers greatly differ and that the habits of the salmon may differ 

 accordingly, should not be lost sight of, and that generaUzations from specific locaUties 

 may lead to confusion. While the basic physiological impulse to ascend fresh- water 

 rivers is doubtless the same in aU salmon, it may be modified more or less by local con- 

 ditions and the necessities imposed by those conditions. Or, as succinctly expressed by 

 Gurley (1902, p. 422), the habit of abstinence from food 'has many degrees and probably 

 is strict in direct ratio to the length of time required ad minimum and the amount of 

 time available ad maximum, for the species to reach the spawning grounds,' and so 

 'Natural selection would then gradually weed out those individuals which had the feed- 

 ing impulse strong, and favor those which tended to concentrate their feeding and motor- 

 sexual functions into different portions of the yearly cycle.' 



It has previously been suggested that with the Atlantic salmon there may be some 

 local structural racial differentiation, something hke that manifested by some of the 

 Pacific salmon, as shown by Gilbert (1918, p. 37). Or, there may be a correlated physio- 

 logical differentiation. In fact, this is to be expected. The salmon which ascend the 

 Rhine 500 miles or more have conditions to meet which do not obtain in the com- 

 paratively short rivers of Scotland or Norway. Fish which Uve in the Baltic and ascend 

 the rivers of Finland or Sweden can hardly be comparable in every respect with those 

 which ascend the Rhine or the rivers of Great Britain. While in the case of aU, the 

 'feeding and motor-sexual functions' are largely 'concentrated in different portions of 

 the yearly cycle,' the degree of concentration and the abruptness of transition from the 

 one to the other may and probably do differ according to conditions. Furthermore, it 

 could hardly be expected that in any case would a sudden suppression of the feeding 

 impulse take place. The switch-board of the 'nerve responsive' mechanism could 

 hardly be expected to be under such complete automatic control. So while the breeding 

 impulse more or less gradually becomes paramount, and the feeding impulse correspond- 

 ingly subordinated to it, it may be expected that the nerve mechanism may be for a 



