Chap. VIIL] AND OF AMPHIBIA. 123 



number of fishes become swollen into distinct ganglia at 

 their point of junction with the Medulla, and in some — • 

 such as the Carp, the Torpedo, the Electric Eel, and the 

 Skate — these lateral ganglia, situated at the side of the 

 cerebellum, are exceptionally large. The Glosso-pharyn- 

 geal is in reality only a large separate branch of the 

 vagus. In some fishes it joins one of the roots of the 

 vagus ; and, even where this external junction does not 

 exist, an internal union is effected by the smaller nerve 

 entering the nucleus of the larger one. 



A little anterior to the ganglia of the Vagi, large 

 swellings are also frequently met with in connection with 

 the roots of the Trigeminal nerves (fig. 10), which in 

 fishes are mostly very large, and have an extensive dis- 

 tribution even beyond the region of the head. The 

 remaining sensory nerves of the medulla — the Auditory — 

 are attached to it by tw^o or three roots, between the vagi 

 and the 5th nerves. These nerves are large, though it 

 is only rarely that a distinct ganglionic swelling is found 

 at their point of junction with the medulla (fig. 11). The 

 ganglia are usually embedded in the Medulla itself, and 

 some of its roots soon join another large ganglion : 

 viz., the Cerebellum. This apparent connection of the 

 auditory nerves with the great motor ganglion in Verte- 

 brates, whatever its explanation may be, is quite in har- 

 mony with the close relation of the * auditory saccules ' 

 and nerves to the pedal ganglia in Mollusks, and with 

 their relation to the most active motorial centres of the 

 ventral cord in those Insects (such as Locusts and Grass- 

 hoppers) in which the so-called * auditory saccules ' have 

 been positively detected.* 



* The Organs of Hearing in Fishes are always double, as in 

 invertebrate animals. They are, moreover, situated within the 

 body, and mostly have no connection with its surface. Sometimea 



