TSE INSTINCT AND SENSES OF FISH. 237 



"We have yet to learn that Nature has imposed 

 upon fish any duty or desire of exploration, beyond 

 those requisite for food and reproduction. There 

 would not appear to be any particular reason why fish 

 should travel farther than necessary for their require- 

 ments ; so when they do travel far, the probable expla- 

 nation is that their requirements cannot be satisfied 

 nearer at hand. 



It is established that, as a general rule, salmon re- 

 turn from the sea to the river in which they were bred, 

 or have subsequently spawned, which is by many con- 

 sidered a most curious trait ; but if it were ascertained 

 that fish during their visit to the sea remained in tlic 

 vicinity of the estuary, the coincidence would be 

 robbed of much that is marvellous. 



By his sojourn in tidal waters the salmon loses the 

 parasites contracted in fresh water, and gains food to 

 give him condition and increase of size ; so if it should 

 so happen that he can satisfy these requirements while 

 skirting the estuary, he possibly might feel disinclined 

 to wander farther afield. 



When a creature is weak and in wasted condition, 

 great exertion is distasteful, restoration to health and 

 strength being the first prompting of nature. 



The idea that salmon travel thousands of miles 

 between their periodical visits to fresh water, no doubt 

 is most romantic ; but for all that it may not be correct 

 as a general rule, although that occasionally they make 



