FLAT-FISHES 



79 



towcards the middle line, and turning caudally run parallel to the 

 ventricle before entering the facial lobe, the identity of which is 

 thus established. The somatic-sensory lobes completely envelop 

 the facials and are readily recognised by tlieir histological structure ; 

 they extend far in a cephalic direction and increase in size so as to 

 form two prominent bulges which appear in the naked eye view. 



PLATE 14.— Two Sections of Brain of Sole. 



n amb 





VII. — Facial nerve, c.l.m. — Cerebellum, c.a.l. — Central acoustic lobe, s.s.l. — 

 Somatic-sensory lobe. f.l. — Facial lobe, n.amb. — Nucleus ambiguus. g.l.s.g.t. 

 — Great longitudinal secondary gustatory tracts, d.f.f.l. — Descending fibres 

 of facial lobe. 



The acoustic tubercles are large. At the base of the cerebellum and 

 at first separate from it is a broad bandof tissue roofing the ventricle 

 on the inferior margin of which are to be seen groups of round cells 

 Mith tranversely rurming fibres dividing them ; this is similar to 

 the areas which have been described in the cyprinoid brain and 

 which we have associated with an auditory function. This central 

 acoustic lobe has been seen in the herring and mormjTus, both of 

 which have an elaborate auditory organ ; it is well-marked in surface 

 feeding cyprinoids, but is rudimentary in bottom feeding species. 

 How are we to account for its presence in such a typical bottom- 

 feeder as the sole which, moreover, has no sound producing organ. 



