ENCEPHALON OF FISHES. 



275 



Herring, fig. 184, c ; but sometimes covering only a small portion, as 

 in the Chub, fig. 177, c, the Lump-fish, and the Lepidosteus, fig. 

 174, c. The relative size of the cerebellum, accordingly, varies 



175 



176 



Brain ; 



Ll'l>idii:-U'US 



Brain ; Amblyopsis 

 magnified 



Brain; Eel. ecu. 



greatly in different bony fishes ; it is very small in the lazy Lump- 

 fish, and extremely large in the active and warm-blooded Tunny, 

 where, also, its surface shows transverse groovings. 

 The cerebellum is unsymmetrically placed in the 

 Pike and some Flat-fish (Pleuronectidoe), and is 

 unsymmetrically shaped in the Sharks : it presents 

 a longitudinal groove in the Diodon, and a pos- 

 terior notch in the Herring : a transverse notch di- 

 vides it into an anterior and posterior lobe in the 

 Lophius : it bears a crucial depression in the Skate. 

 The cerebellum presents in many fishes a small 

 cavity or fossa at its under part, continued from 

 the fourth ventricle, fig. 178, c: it is solid in the 

 Tench, the Garpike, and the common Eel : some 

 grey matter is usually found in its interior, with 

 feeble indications of white striae ; but there is no Brain and portion of 

 * arbor vita.,' except in the Tunny and Sharks. ^™ of 



The posterior ' crura cerebelli ' are formed by 

 the posterior pyramids, fig. 172, d, with part of the restiform 

 tracts, ib. c ; vertical fibres from the sides of the cerebellum 

 continue to attach it to the 

 sides of the restiform or triffe- 

 iminal lobes, and some of these 

 are continued as arciform fila- 

 ments upon the under surface 

 of the medulla oblongata : they 

 answer to the ( crura cerebelli ad pontem ' of Mammalia ; but, as 



T 2 



Section of Brain, Carp 



