30 SUPPLEMENT ON 



Hence the external senses of fish cause few lively and 

 distinct impressions ; nature must appear indistinctly around 

 them : their pleasures can be but little varied ; the sufferings 

 which they may have to apprehend from without, nothing 

 more than pain from actual wounds. The want which, 

 excepting in the season of love, causes all their activity, must 

 be the sensations resulting from hunger. When not engaged 

 in reproducing the species, their predominant passion to 

 devour, almost their sole occupation. Their entire conforma- 

 tion, all their organs of motion, appear intended for that 

 purpose alone. To pursue a prey, or to escape a destroyer, is 

 the constant occupation of their lives ; determines their choice 

 of residence ; is the principal object of the differences of form 

 among them, and the intention of the small portions of 

 instinct and of artifice, which nature has conferred upon some 

 of the species. The angling filaments of lophii the exten- 

 sile jaws of epibuli and corici l the terrible electrical shocks 

 caused by torpedos and gymnoti, have no other object. 



Fish are but slightly affected by the variations of tempera- 

 ture; not only because the changes are less in the element 

 they inhabit, than in our atmosphere, but also because their 

 bodies, assuming the temperature of the surrounding fluid, the 

 contrast of external cold with internal warmth scarcely exists 

 for them 2 . Hence the seasons are not the exclusive regula- 

 tors of their migrations and periods of propagation, as they 



1 Sparus Insidiator of Pallas, and some species of the genus lutjan of 

 Risso, &c. all endowed with the power of suddenly projecting their jaws 

 almost half their own length beyond the head. 



2 It has been observed by Dr. Armstrong, of the Royal Naval Hospital, 

 Plymouth, that the temperature of fish is not only lower than that of the 

 sea at the surface, but varies considerably in different individuals of the 

 same species. On the banks of Newfoundland, 3rd September, 1829, when 

 the temperature of the air was 66, and of the water at the surface 64 

 Fahrenheit, a thermometer placed on the abdomen of nine cod-fish drawn 

 up in succession from a depth of forty fathoms, indicated the following 

 degrees of temperature, viz. 37% 46" 41, 35, 36, 40, 39", 38^, 36i. 



