FLAT-FISHES 81 



If tliis eoiu'Iusioii is accepted it would appear that the sole feeds 

 by tiuicll, touch, and hearing, represented centrally in olfactory, 

 somatic-sensory, and central acoustic lobes, all of which are remark- 

 ably developed. 



AVe have noted the very small facial lobes of the sole and the 

 slight development of the gustatory system. The olfactory organ 

 must now be described in detail. The striking similarity of the 

 olfactory organ of the sole to those of the conger and the eel has been 

 described by Bateson, " the plates are arranged in two rows on each 

 side of a central raphe upon which the two rows are folded longi- 

 tudinally, so as to form a lining to the olfactory tube. The raphe 

 in the sole is depressed so as to form a groove from which the plates 

 rise up." 



Associated with this similarity we find that the olfactory bulbs 

 and lobes of the conger, eel, and sole present a very similar pattern. 

 " In front of the medulla of the eel, Anguilla vulgaris, the several 

 regions of the brain are of approximately the same size and each is 

 more or less clearly bilobed, the brain appears to consist of four 

 pairs of rounded equal-sized nodules. The anterior pair (olfactory 

 bulbs) are slightly pointed in front, and give off two large olfactory 

 nerves. The thalamencephalon is remarkably long for a teleostean 

 forming a narrow neck between the cerebrum and the optic lobes, a 

 descrijition which applies almost equally to the condition found in the 

 sole." The diet of the sole must now be referred to and its relation 

 to its brain pattern considered. The sole is nocturnal in its habits and 

 is caught more frequently at night than by day : and in the daytime 

 more frequently when the water is cloudy than when it is clea 

 The sole seeks its food more by sense of smell and touch than bj 

 sight and in the Irish Sea prefers worms (nereids) to any other form 

 of chet. (Jenkins, 1925.) According to Cunningham, " the sole 

 is a distinctly shoal-water fish. The stomachs of 36 soles were 

 examined and in 18 the food consisted of marine worms. Small 

 fragments of the shells of bivalves were found, but these seemed to 

 be, in most cases, to have been attached to the tubes of tube- 

 building worms, although small bivalves were sometimes found 

 entire. The throat-teeth are pointed and slender and cannot serve 

 for crushing shells as do those of a plaice. 



" Twenty-five per cent, of the stomachs contained echinoderms, 

 mostly sand-stars, Crustacea were found in two per cent. In 

 soles caught off the west coast of Ireland it was found that worms 

 were most frequent, then echinoderms, then molluscs, then crusta- 

 ceans, and lastly fish in a few cases. The echinoderms were mostly 

 brittle-stars or sand-stars : among the moUuscs were small speci- 



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