FLxVr-F18HES 85 



band and jiass ventrally and outwards into the great lateral secondary 

 gustatory tracts. JNloro caudally the motor nucleus of the tenth nerve 

 or the nucleus ambiguus appears, but the vagal lobes are of a very 

 moderate size. The great difference in size between the facial lobes 

 of the i)laice and those of the sole is no doubt to be associated with 

 the ])resence of taste-buds in the plaice, which are numerous, as 

 their description by Bateson makes clear. 



PLATE 15. 





V- 



\/ / 



•i^li. 



Transverse sections across the optic lobes of (left) Sole, and (right) Plaice. 



Note the greater size of the tecta optica in the Plaice and its convoluted form- 

 l.i. — Lobus inferior, n.r. — Nucleus rotundus. s.v. — Saccus vasculosus. 



There is no central acoustic lobe or area. Bateson, in writing on 

 the olfactory organ of Pleuronectes, states that the plaice, flounder, 

 lemon sole, and dab, as well as the halibut, " have only one row of 

 olfactory plates arranged in a single series in a direction parallel 

 to the long axis of the body and not transversely to it." This is in 

 sharp contrast with the condition that is found in the sole. 



The lemon sole has a brain of similar external appearance to 

 that of the plaice. The primitive end- brain is rather larger than 

 in the plaice and the optic lobes are large ; they do not, however, 

 possess the bi-lobed character of those of the plaice, nevertheless, 

 there is a distinct lateral bulge anteriorly on either side. The 



