NERVOUS SYSTEM. VERTEBRATA. 83 



that of Scyltium (D. 73), the most noteworthy being the 

 relatively small size of the cavities of the optic lobes, the 

 more massive structure of the cerebellum, and the absence 

 of a cavity in its anterior lobe. 



Upon the right side, the posterior lobe of the cerebellum 

 has been removed to show the complicated folding of the 

 medullary auricle and its passage into the longitudinal zone 

 of the cerebellum. The olfactory bulbs and the greater 

 part of the peduncles have been removed. Transverse 

 sections of them are mounted above to show that they 

 do not contain a cavity. 



D. 84. The cranium of a Torpedo {Torpedo galvanii) opened 

 from above to expose the brain. A pair of immense 

 electric lobes form the most striking and important feature 

 of the brain; they are developed in the floor of the medulla, 

 and apparently represent the motor vagal lobes of other 

 Elasmobranchs in a state of excessive hypertrophy. Pro- 

 jecting upwards, they entirely fill and obliterate the rhomboid 

 fossa and are bounded anteriorly by the auricles and 

 cerebellum. Each gives rise to two large bundles of 

 nerves for the electric organ. The electric lobes contain a 

 number of gigantic ganglion-cells, the axis-cylinders of 

 which pass directly into the electric nerves. The brain, 

 with the exception of the electric lobes, is poorly developed. 

 The cerebellum is very small, diamond-shaped, and, but 

 for a cruciform furrow, smooth. The optic lobes are of 

 moderate size, although the nerves are remarkably slender. 

 The cerebrum is globular, with slight prominences on its 

 dorsal surface ; it receives at its antero-lateral corners a pair 

 of fine solid olfactory peduncles. 0. 0. 1310. Hunterian. 

 Rohon, Arb. Zool. Inst. Wien, t. i. 1878, p. 151. 



HOLOCEPHALI. 



D. 85. Two specimens of the brain of a Sea-Cat (Chimcera 

 monstrosa). In the lower specimen the brain is seen in situ 

 from above, the hypothalamus and neighbouring parts being 

 also exposed through a window cut in the cranial floor. 

 In the upper specimen the internal structure is shown by 



