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" hypoglossal " nerve, or first spinal, Init we do not con- 

 sider this to be a cranial nerve in fishes. 



3. Communis (Yiscero Afferent?) System. — Partly 

 synonymous with the fasciculus communis system of 

 Osborn and Strong-. A striking feature about this sensory 

 system is that it may innervate both ecto- and endo-dermal 

 surfaces, and it may therefore be disputed whether it is a 

 visceral nerve that has invaded the skin, a somatic nerve 

 that has invaded the visceral surfaces, or a complex of 

 more than one component. The latter seems perhaps the 

 most probable. The fibres of the communis system are 

 fine and lightly myelinated, and are distributed 

 peripherally as follows : — (a) to the special sense organs in 

 the outer skin called " terminal buds," i.e., to all the 

 definite sense organs of the skin not belonging to the 

 lateral line system. This part of the component has been 

 reduced in the plaice ; (b) to taste buds in the mouth ; 

 (c) to the general mucous surfaces without the interven- 

 tion of sense organs at all. The ganglia and cranial 

 nerves into which the system enters are : (a) the genicu- 

 late ganglion (vii.), glossopharyngeal ganglion (ix.), and 

 the intestinal and four branchial ganglia of the vagus (x.). 

 Any communis fibres in the trigeminus arise from the 

 communis facialis. The central origin of the component 

 is the Lobus vagi, and the enormous vagal lobes of 

 Carpiodes are simply due to the hypertrophy of the com- 

 munis vagi component in this fish (Herrick). Further the 

 so-called Lobus trigemini of some fishes (Amiurus) is due 

 to the hypertrophy of the communis facialis, and hence it 

 should be called Lobus facialis. 



4. Yiscero Efferent System. — This comprises the 

 motor roots of the vth, viith, ixth and xth cranial nerves. 

 Each of the first two has its own motor nucleus in the 

 brain, but the two latter arise from collections of cells 



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