Hkrrick. ^for/>/n)/o<^^']' of Brain of Bony Fishes. 221 



logically. The mesaxial lobe is characterized by small flask- 

 cells, with large granular nuclei and dense nucleoli. They 

 are very closely packed, with a strong tendency toward 

 a zonary arrangement. The lateral lobe is characterized by 

 similar elements more sparingly distributed, but still show- 

 ing an evident zonary arrangement. This latter is particu- 

 larly true ventrally. Dorsally the cells are less numerous, 

 and those of the type found in the central lobe predominate. 

 The central lobe lies between the two last mentioned and 

 typically does not appear on the dorsal surf:ice, being tri- 

 angular with the apex directed dorsad. The cat fishes, how- 

 ever, present a marked exception to the latter point. The 

 histological elements are large cells lying in a clear stroma. 

 They are spindle-shaped or multiangular, all with very large 

 processes, large circulr nuclei and dense nucleoli. The 

 central lobe is nowhere sharply separated from the lateral 

 lobe. On the other hand, the frontal fissure separates it very 

 clearly from the mesaxial lobe, especially peripherally. The 

 structure of the occipital lobe closely resembles that of the 

 central, while the temporal lobe has the small cells of the 

 mesaxial, somewhat less abundant, but with the same zonary 

 arrangement. 



The prosencephalon, as a whole, is considerably larger 

 than the optic lobes, but very much smaller than the cere- 

 bellum. It attains to about the average size as compared 

 with other Teleostei thus far examined. 



Diencephalon . — The thalamus in the adult cat fish is 

 entirely hidden from the dorsal aspect by the optic lobes and 

 the cerebellum. Even the attachment of the epiphysis is 

 obscured by the forward extension of the cerebellum. The 

 epiphysis is very much as in some Lacertilia. It arises as a 

 small membranous tube lined with epithelium immediately 

 cephalad of the superior commissure, passes dorsad en- 

 wrapped by the plexus which fills this region, then turns 

 abruptly cephalad passing under the cerebellum and over the 

 cerebrum. Tt lies in the shallow median fissure in intimate 



