FISH MIGRATIONS. 249 



which its anal fin is provided ; it then pushes itself up- 

 wards by straightening the tail, while it closes the gill- 

 covers not to prevent progress, and so on. Sir E. Tennent, 

 however, without disputing the evidence that these fish 

 do climb trees, says, 



The probability is, as suggested by Buchanan, that the 

 ascent which was witnessed by Daldorff was accidental, and 

 ought not to be regarded as the habit of the animal. 1 



A great number of species of fish perform migrations. 

 In relation to intelligence, the most interesting of these 

 is the migration of salmon, which annually leave the sea 

 to spawn in rivers, though there is some doubt whether 

 the same individuals spawn every year. There is no doubt, 

 however, that the same individuals frequently, though not 

 invariably, revisit the same rivers for their successive 

 spawnings. This fact may be due either to the remem- 

 brance of locality, similar to that which is unquestionably 

 manifested by birds, or to the salmon not swimming far 

 along the coast during other seasons of the year, and there- 

 fore in the spawning season when seeking a river happen- 

 ing to hit upon the same one. The latter hypothesis is 

 one which Mr. Herbert Spencer tells me he is inclined to 

 adopt, and, being a salmon-fisher, he has paid attention to 

 the subject. He informs me of an observation by a friend 

 of his own, who saw a salmon, when about to spawn, swim- 

 ming along the coast-line, and all round a boathouse, 

 apparently seeking any stream that it might first en- 

 counter. 



The distances up rivers to which salmon will swim in 

 the spawning season is no less surprising than the energy 

 with which they perform the feat, and the determination 

 with which they overcome all obstacles. They reach 

 Bohemia by the Elbe, Switzerland by the Rhine, and, 

 which is much more wonderful, the Cordilleras of America 

 by the Maragnon. 



They employ only three months in ascending to the sources 

 of the Maragnon (a journey of 3,000 miles), the current of 

 which is remarkably rapid, which is at the rate of nearly forty 



1 Natural History of Ceylon, p. 351. 



