Herrick, Morphology of Brain of Bony Fishes: 31 



structure and disappear at the level where the conus prfficomis- 

 suralis becomes most prominent. These may conveniently be 

 termed i\ie post-cinerea and seem to have no homologues in other 

 groups. At the higher levels they fuse with the nidulus niger, 

 but never seem to contain other elements than the small 

 " Deiters' corpuscles" imbedded in a dense stroma which stains 

 deeply and homogeneously. The conus praecommissuralis of 

 Fritsch lies between these masses and cephalad of the post- 

 perforata (substantia perforata posterior) which, as mentioned by 

 C. Judson Herrick above, ^ is a constant point characterized by 

 the presence of a large vessel. Fritsch homologized this with 

 the interpeduncular body, but I am obliged to agree with May- 

 ser, that it does not receive the fibres of Meynert's bundle 

 which pass on to enter the post commissuralis. The latter is 

 therefore the specific homologue of the interpedunculare The 

 present structure is devoid of ganglion cells and consists of a 

 meshwork of fibres and Deiters' corpuscles. It may be regarded 

 as a nutritive region like that of the prteperforata. It might be 

 supposed that the post-cinera were also in some way associated 

 in the nutritive processes. 



4. The infundibular region and hypophysis. A great deal of 

 unnecessary trouble has arisen in the interpretation of structures 

 which have unmistakable homologies in all vertebrate classes. 

 The tuber cinereum is well-developed and completely distinct 

 from the hypoaria and stands in perfectly normal relation to the 

 corpora albicantia (mammillaria) and to the hypophysis. The 

 latter is constructed on a plan similar to that in mammals, except 

 that two portions which have a distinct origin are in the latter 

 group partly combined, while in fishes they remain distinct. 



In the drum {Haploidonotus) our series of perpendicular 

 sections gives a complete idea of the connections of the axial 

 portion, or saccus vasculosus. The relations with the cinereum 

 are two-fold. The dorsal surface of the saccus lies closely ap- 

 pressed to the caudo-ventral aspect of the cinereum. From the 

 point of structural union at the extreme caudo-ventral point 

 there passes into the saccus. a rather strong stalk of fine fibres 



iC. Judson Herrick. Contributions to the Morphology of the 

 Brain of Bony Fishes. I. — Siluridse. Vol I, p. 223. 



