2i6 SALT-WATER FISHES 



During the greater part of their life, when full-grown, 

 these flat-fishes reside close to the bottom, lying, in fact, in 

 the sand or gravel, which often affords them a high degree 

 of colour-protection. Cunningham gives in his monograph 

 an admirably coloured plate of a sole lying in gravel ; but 

 an even more striking approximation of the fish to its 

 surroundings may sometimes be seen in aquarium tanks, 

 and the writer has seen more wonderful examples of this 

 at the Plymouth tank-house. Allusion has already been 

 made to the variation in colouring in this group.* As 

 long as the fiat-fish lies on the bottom, its colouring is 

 of great service to it. Occasionally, however, even large 

 dabs or turbot are seen swimming near the surface, and in 

 such a position they are peculiarly conspicuous. The largest 

 halibut and turbot prey on fish, but the rest feed on worms, 

 molluscs, and crustaceans, which are sucked into the twisted 

 mouth and seized in the small, sharp teeth. The fins are 

 without spines (which is also the case in many round fish, 

 such as cod and herring), though the plaice and lemon dab 

 have a sharp spine before the anal fin. 



All the flat-fishes of our coasts lay floating eggs, even 

 the flounder of our rivers going down to the sea to deposit 

 its eggs in salt water, like the eel. Here we have a converse 

 case in respect of the habits of the salmon. That fish comes 

 into fresh water, apart from all question of ancestral habitat, 

 in order that its egg may sink in the shallow fresh water 

 and lie safe in the furrows that it makes for the purpose. 

 The flounder, on the other hand, could not possibly lay 

 its buoyant egg in the tidal waters of rivers if it were 

 essentially a fresh-water fish, for the eggs would inevitably 

 be carried down to the sea, and the salt water would kill 

 the embryos. The groups under notice must be regarded as 

 closely related to the cod family, described in an earlier chapter. 



* See also Mcintosh in Ann. and Mag. Nat. Hist., April, 1902, p. 291 

 and Patterson in Trans. Norf. and Norm. Nat. Soc, 1891-2, p. 326. 



