326 SOFT-FINNED ABDOMINAL FISHES. 



their gills with proper play, and in a few moments they 

 expire. 



To some fishes bred in "the sea, fresh water is im- 

 mediate destruction ; and, on the other hand, many of 

 those which have been bred in lakes and ponds cannot 

 bear the salt-water to come in contact with their skin ; 

 whilst the salmon, the shad, the smelt, and the floun- 

 der, annually quit their native element, and come up 

 our rivers to deposit their spawn. This seems the most 

 important business of their lives ; and there is no dan- 

 ger they will not encounter to find a proper place for 

 the deposition of their future offspring. The salmon, 

 upon these occasions, is seen to ascend rivers five hun- 

 dred miles from the sea; and not only to brave the 

 danger of various enemies, but also to spring up cata- 

 racts as high as an house. It sometimes happens, how- 

 ever, that, they want strength to make the leap ; then 

 in our fisheries they are taken in their descent, either in 

 nets or baskets, placed so as to prevent their retreat. 



Though these fish take very long voyages for the pur- 

 pose Of depositing their spawn in some fresh-water 

 stream, there are others that are known to quit their 

 residence in rivers for the purpose of bringing forth 

 their young in the sea ; and there are others that reside 

 entirely in the ocean, which annually migrate many 

 thousand miles. Of this kind are the cod, the haddock, 

 the whiting, the mackarel, the tunny, the herring, and 

 the pilchard. The stated returns and regular progress 

 of these fish of passage is one of the most extraordinary 

 circumstances in the history of Nature : what it is that 

 impels them to such distant voyages, what directs their 

 passage, and what supports them by the way, curio- 

 sity may ask, but philosophy can hardly resolve. 



The cod seems to be the foremost in this wandering 



