638 MR FRANK J. COLE ON THE 



of the vagus of higher vertebrates with a lateral line nerve fall to the 

 ground.* 



(4) There is a tendency on the part of the lateral line nerves to arise, both in the 



embryo and in the adult, by the splitting of a single trunk. Strong found 

 that the superficial ophthalmic, buccal and lateral line division of the 

 hyomandibular (facial) all arose from a single trunk in Amphibia. Pollard 

 (60) describes facts of a similar character. For example, he finds that in 

 several forms of Siluroids the superficial ophthalmic and buccal divisions of 

 the Vllth arise in the adult from a single trunk. The same is described 

 for Elasmobranch embryos by Van Wijhe and Beard. A partial common 

 origin is described by Ewart in Lcemargus, whilst a more marked form will 

 be presently described in Chimsera. 



(5) All the lateral line nerves have a single common internal origin in the brain 



(" tuberculum acusticum"), from which none of the other cranial nerves 

 arise (Strong). This common origin, pending further investigations, must 

 be associated with the facial nerve, but its morphological relations may not 

 be with any of the cranial nerves. Each of the four great divisions of the 

 system (superficial ophthalmic, buccal, external mandibular, and lateralis) 

 may have a separate external origin from the brain, and therefore the fact 

 that the lateralis has a separate root is of no special significance, whilst its 

 position on the medulla points to its common internal origin with the other 

 lateral line nerves. The connection between the lateralis and the vagus, 

 therefore, is more apparent than real, and its relations to the vagus must 

 have been secondarily acquired, and correspond to the confusion of the 

 buccal nerve with the maxillary division of the Vth.t 



(6) Each of the four lateral line nerves has its own ganglion, and these ganglia are 



quite distinct from the ganglia of the cranial nerves sensu strictu. 



It is now necessary that the apparent exceptions to the above view should be 

 discussed. Believing as I do that no innervation of sensory canals from the trigeminal 

 nerve will bear investigation, — and I hardly think it will be doubted that all the evidence 

 of any reliability points to this view, — my own statement that two sense organs of the 

 supra-orbital canal are innervated by twigs from the profundus cannot be considered of 

 any importance. Stannius first proved, and proved conclusively, that fibres from one 

 cranial nerve may accompany the branches of another ; and as Dr Pollard remarks to 

 me in a letter : " I should prefer to say that some nerve fibres had struck the path of 

 the profundus but did not belong to it, just as, for instance, in Siluroids the fourth nerve 



* Strong, in feet, found that the auricular nerve of the adult was not the metamorphosed lateralis, which is 

 surely what was to be expected, seeing that the auricular nerve consists of somatic fibres ! 



t In this connection the anastomosis of the facial with the lateralis, as described by Ahlborn in Petromyzon (32), 

 acquires a special significance, as if its facial origin were special sensory, it might not unreasonably be held to be the 

 primitive root of the lateralis. Op. Spencer, Quart. Jour. Micros. Sci., 1885. 



