lur, 



one woultl i'X]>0('l, seeing' that it is cuunt'ctcd with llio 

 yciu'ial activity of the orgauisin, and the IMaiee is slugg'ish 

 in liahits. 



Tlie 111 id-bra in is represented on the dorsal surt'aee on 

 each side by the tectum ojiticum (optic h)be). These are 

 ^erv h\rg-e bodies almost spherical in shape, and charac- 

 terised ill dead and preserved specimens, and doubtless in 

 life also, by a deep furroAv, which extends backwards in a 

 curve from the anterior margin of each lobe for about half 

 its aiitero-posterior diameter. 



As is usual in Teleosts, the 'tweeii-braiii liardly 

 appears at all on the dorsal surface of the brain, being 

 excduded from it by the meeting of the two striata and 

 optic lobes. However, a small portion of its membranous 

 roof is visible, and from this there is seen emerging by 

 the triangular space formed immediately in front of the 

 median apposition of the two optic lobes, the extrenieh' 

 line pineal tube. In sections it is seen to arise as an 

 evagination of the roof of the third ventricle almost 

 behind the ganglia habenuhe and in front of the posterior 

 conimissure. It then passes foiwards over the pallium of 

 the left striatum and swells into the large pineal gland 

 lying on the pallium near the anterior extremity of the 

 left striatum. By pressing apart the optic lobes there 

 ma}' be seen immediately in front of the exit of the pineal 

 tube the ganglia habenuhe and the plaited choroid rt)of of 

 the third ventricle. 



In a well-preserved brain the membianous pallium of 

 the foic-brain is very obvious. It is a large oval sheet, 

 with its long axis al right-angles to that of the lirain, and 

 almost (Mjual to that of the optic lobes. It is a very thin 

 membrane, and appears thicker than it really is on account 

 of the coagulated cerebro-spinal Huid in the ventricle. 

 The corpora striata are also visible through the pallium. 



