384 W. H. GASKELL. 



epi-cliordal portion. The epicliordal portion terminates in a 

 projecting prominence, termed by Fritsch the conus post- 

 commissuralis, and recognised by Ahlborn as the region 

 of the ganglion interpedunculare. The ventral appearance of 

 the brain is shown in PI. xiii, fig. 6, of Ahlborn's paper (3) 

 after removal of the hypophysis and saccus vasculosus. If the 

 brain is carefully dissected out so as to leave the saccus vascu- 

 losus intact^ and then examined in the fresh state, it is seen 

 that the projection formed by the infundibular region, and 

 also that of the conus post-commissuralis, stand out most 

 prominently from the rest of the nervous material owing to 

 their peculiar appearance : instead of appearing white and 

 opaque like the rest of the nervous matter, they look like 

 transparent jelly-like masses imposed upon the opaque white 

 mass of the rest of the brain ; so transparent is the material 

 here that the brain-cavity shows through, as can be imagined 

 from the inspection of Ahlborn's fig. 6. 



Further, the brain lies in a mass of glandular-looking 

 material composed of cells, and characterised by the amount 

 of pigment which ramifies between the cells. This tissue 

 cliags largely to the brain when it is dissected out, so that the 

 surface of the brain presents an appearance as in PI. XXV, 

 fig. 1. This thick glandular material is arranged in a 

 definite manner on the surface of the brain ; it forms a 

 bilateral pigmented cellular organ, which may be looked upon 

 as forming two lobes symmetrically placed on each side of the 

 ventral constriction which marks the separation between the 

 epi- and pre-chordal portions of the brain. From here, as 

 starting-point, the tissue spreads in a fan-shaped fashion over 

 the lateral portions of the epicliordal brain, never reaching 

 the mid-line dorsally, but stopping short at the choroid plexus 

 iii. In the prechordal portion it passes towards the dorsal 

 surface, round the infundibular projection, up to the choroid 

 plexus ii, and surrounds the pineal eye and cerebral hemi- 

 spheres, so as to fill up the brain-cavity anteriorly to the 

 nervous system. In most of the sections I have shown the 

 arrangement and structure of this tissue. 



