88 BRAIN AND BODY OF FISH 



an oil-globule. It should be remarked that the dentition of the 

 plaice is well adapted for crushing shellfish : this is in great con- 

 trast with the teeth of the sole. 



Writing on the bottom fauna and food of fishes, Stevens describes 

 the feeding behaviour of the lemon sole, which depends on eyesight 

 to discover its prey, and forages principally by day. At Plymouth 

 its diet is solely marine worms and annelids, " Tubiculous annelids, 

 unless hunted discreetly, disappear to safety down their holes. The 

 lemon sole is always on the move. It comes to rest in a character- 

 istic attitude with the head and fore part of the body raised well off 

 the bottom. Remaining perfectly still in this position, it scans the 

 ground with its very prominent and movable eyes. Should it then 

 spy a worm, cautiously emerging from its burrow, it pounces upon 

 it with a kind of forward leap, bringing its mouth down almost 

 vertically upon its victim by a strong arching of the anterior part 

 of the body." The plaice and dab behave in a similar manner 

 when searching for food, but they do not raise the head quite so 

 high before they pounce. 



The plaice feeds chiefly on bi valve shell-fish, whose shell it is 

 easily able to crush by means of the strong blunt teeth in its throat, 

 but it also eats sea-worms. In the Firth of Forth, the most common 

 food was a small species of bivalve called Scrobicularia, and next in 

 frequency was the razor shell, Solen ; cockles and clams were also 

 present. Of the worms all kinds were devoured, sea-mouse, lug- 

 worms, rag-worms and tube- worms. Sand stars were sometimes 

 eaten, and an occasional sMmp, but fish very rarely. The witch 

 favours marine worms ; they were present in 72 per cent, of the 

 stomachs examined ; Crustacea, 30 per cent. ; molluscs in 14 per cent, 

 and echinoderms in only 3 per cent. Dabs feed mostly on Crustacea. 

 These occurred in 48 per cent, of the stomachs. Next in abundance 

 were echinoderms, namely, sand-stars and brittle stars, which 

 amounted to 21 per cent. Molluscs were less common and worms 

 occurred in only 16 per cent, of the specimens ; sand-eels and small 

 herrings in only 5 per cent. 



The members of this group are, therefore, bottom-feeders, and 

 their type of brain accords with their mode of hunting. The 

 olfactory lobes are but moderately developed, but the optic lobes 

 are large as also the facial lobes, the somatic-sensory lobes are less 

 prominent as one would expect in fish which are not predacious. 



The third group of flat-fishes belong to the family known as the 

 Scophthalminse, according to Norman's classification, and the com- 

 mon British flat-fishes belonging to this family, that will now be 

 described, are three, two belong to the genus Scophthalmus, namely, 



