114 



supposed to represent the nucleus amhig'uus. The fibres 

 of this system are heavily myelinated. 



5. Acustico Lateral System. — Includes the auditory 

 and lateral line nerves. Let it he emphasised at once, 

 what is taking a long time to filter down into the text- 

 books, that the lateral line nerves can only be associated 

 with two cranial nerves^ — the viith and xth. The lateral 

 line fibres in the fifth nerve are always derived from the 

 facial, those in the ixth (when jiresent) from the vagus. 

 The fibres of this system are distributed to the ear, to the 

 sense organs in the lateral line canals, and to those lateral 

 line sense organs lying free on the skin, and known as 

 pit-organs. Its ganglia are the dorsal and ventral lateral 

 ganglia of the facial, and the lateralis ganglion of the 

 vagus, and its fibres are very large, being in fact the 

 coarsest in the body. Its cential termination is the tuber- 

 culum acusticum of the antero-dorsal region of the 

 medulla — associated with the cerebellum. The hyper- 

 trophy of the lateral line nerves produces an exaggeration 

 of the tuberculum acusticum well marked on the surface 

 of the brain and called by .Johnston the Lobus linese 

 lateralis. This lobe has also been called the Lobus trigemini 

 by the older writers, and when associated with lateral line 

 fibres it may well receive the name given it by Johnston. 

 Otherwise it should be called the Lobus facialis (see above). 



Nervus Olfactor-iu s* — I. (Figs. 26 and 28.) 



As considerable asymmetry is exhibited by these 



nerves, both sides will be described. 



*For the cranial nerves of Teleostean Fishes compare especially the 

 following works: — Allis (A77iia), Jour. ]Morph., ii. anrl xii. ; Cole (Gadus), 

 Trans. Linn. Soc, ser. 2, vii. ; Desmoulins and Magendie (nerves of 

 RJwmbiis), Anat. Syst Nerveux, Paris, 1825 ; Herrick {Menidia, Gadus, 

 and A7niurus), Jour. Comp. Neurol., ix., x., and xi. ; Juge {Siliirus), Rev. 

 Suisse Zool., vi ; and Stannius (general), Rostock, 1849. The works of 

 Herrick are most important so far as the Plaice is concerned, and should 

 certainly be consulted. We have purposely adopted, as far as possible, the 

 same reference letters, in order that the comparisons may be facilitated. 



