182 ■ FISHES. 



spawn ill the open ocean, or that floating spawn is carried 

 hy currents to a great distance from land; and that such 

 embryoes, which for their normal growth require the con- 

 ditions afforded by the vicinity of the shore, if hatched in 

 mid-ocean, grow into undeveloped hydropic creatures, such as 

 the Leptocephales seem to be. 



Abundance or scarcity of food, and other circumstances 

 connected with the localities inhabited by fishes, affect con- 

 siderably the colour of their muscles and integuments ; the 

 periodical changes of colour in connection with their sexual 

 functions have been referred to above (p. 176). The flesh 

 of many Teleostei is colourless, or but slightly tinged by the 

 blood ; that of Scombridce, most Ganoids and Chondroptery- 

 gians, is more or less red ; liut in l^adly-fed fishes, as well 

 as in very young ones, the flesh is invariably white (anaemic). 

 Many fishes, like the Salmonidce, feed at times exclusively on 

 Crustaceans, and the colouring substance of these Inverte- 

 brates, which by boiling and by the stomachic secretion turns 

 red, seems to pass into the flesh of the fishes, imparting to it 

 the well-known " salmon " colour. Further, the coloration of 

 the integuments of many marine fish is dependent on the 

 nature of their surroundings. In those wliicli habitually hide 

 themselves on the bottom, in sand, between stones or sea- 

 weeds, the colours of the body readily assimilate to those of 

 the vicinity, and are thus an important element in the economy 

 of their hfe. The changes from one set or tinge of colours 

 to another may be rapid and temporary, or more or less per- 

 manent ; in some fishes — as in the Pediculati, of which 

 the Sea-Devil, or Lopldus, and Antennarius are members — 

 scarcely two individuals are found exactly alike in colora- 

 tion, and only too frequently such differences in coloration are 

 mistaken for specific characters. The changes of colours are 

 produced in two ways : either by an increase or decrease of the 



