136 
auditory nerve very early, and indeed almost arises sepa- 
rately from the brain. It gives off a nerve above, which 
is the 
5. R. acusticus ampullz posterioris (7. a. p.).—Is at 
first opposed to the external surface of the glosso- 
pharyngeus, and hes between it and the utriculus, but 
exchanges no fibres with it. It turns upwards, crosses the 
elossopharyngeus just as the latter is bending downwards, 
and becomes attached to the outer face of the lateralis, 
but again does not mingle with it. Still coursing 
upwards it crosses the lateralis, curves outwards over the 
top of the posterior ampulla behind, and, now lying 
externally to the ampulla, bends forwards to reach its 
sense organ. 
The remainder of the posterior nerve is the 
6. R. acusticus lagene (7. /.)—Passes backwards 
over the roof of the saceulus, gives off a bundle to that 
part of its sense organ situated there, and then crosses 
inwards and downwards to supply that part of the sense 
organ situated on the inner wall of the sacculus near the roof. 
The Ramulus acusticus neglectus, with its sense 
organ, is absent in the Plaice. In other fishes the Ramus 
vestibularis, or anterior root=ramuli 1, 2 and 3, whilst 
the Ramus cochlearis, or posterior root=4, 5 and 6+the 
R. acust. neglectus. 
Nervus Gliossopharyngeus—lIX. 
Contrary to the condition found in Gadus and Menidia 
the glossopharyngeus leaves the medulla by only one root. 
This, however, consists of two large bundles, which, on 
being traced into the brain are seen to belong to the 
motor and communis systems. ‘There are no cutaneous 
fibres in the glossopharyngeus. In the two fishes above, 
the motor fibres leave the brain by a separate root. 
