176 MR. F. J. COLE ON THE STRUCTURE AND MORPHOLOGY OF 



trunk, /. e. from the facial jii-ojoer. It jjasses upwards and backwards, and is soon 

 joined by the smaller rootlet wiiich arises from the dorsal or external face of the 

 " trigeminal " ganglion. In neither case could I trace any connection with lateral line 

 fibres. By the union of these two rootlets the anterior root is formed, which passes at 

 first backwards and upw^ards closely wedged in between the pro-otic and the ventral 

 portion of the lateral line ganglion, from which it might easily be thought to arise, 

 but with whicli it is not coniiected. Soon after leaving the lateral line ganglion 

 the anterior root passes almost straight upwards over the cerebellum to reach the 

 parietal, which it perforates obliquely, and then passes outwards and backwards. Whilst 

 passing through the parietal canal it receives and fuses with the posterior root from 

 the vagus. 



Fosterior or vagal root {analomical). — Arises from the vagus by two rootlets — a larger 

 and a smaller, the larger one appearing to arise from the lateralis. Both these rootlets 

 themselves arise from a number of bundles which embrace and arise intracrcmially from 

 tlie root of the vagus just as the latter enters the skull. One of these rootlets sent a 

 very small twig which accompanied the lateralis nerve — this being the only connection 

 observed between the posterior root and the lateralis, ^'one of the fibres of the former, 

 tlierefore, are lateral line fibres, but in- some cases the ylossopharymjeus * contributed a 

 bundle to the root. 



Posterior root {microscopical) . — This is variable even in the same specimen. It arises 

 by two rootlets, as described above, which embrace the root of the vagus not far from its 

 point of issue from the medulla. These two rootlets join and then pass internal to the 

 lateralis nerve, being very closely opposed to it, l)ut witli no exchange of fibres. The 

 root then passes upwards and forwards, and immediately on leaving the lateralis swells 

 into a large ganglion w^hich was not observed in the sections of the anterior root. The 

 j)osterior root then passes upwards to the parietal, where it fuses with the anterior root 

 as previously described. The posterior root may pass external to the lateralis, in which 

 case it begins to swell into its ganglion before leaving the lateralis, so that the ganglion 

 as well as the nerve is closely applied to the lateralis. The connection with the lateralis 

 is very close, and the subsequent central course of the nerve i-equires very careful 

 tracing. 



Connections icith spinal nerves. — The accessory lateral system is connected with the 

 anterior spinal nerves in Teleosts generally, eitlior directly by means of the spinal 

 ganglia, or the dorsal branches of the spinal nerves, or indirectly by means of the 

 branches of the system to the pectoral and pelvic fins {Gadns). As was carefully 

 demonstrated by Swan and Stannius, the branch of the system to the dorsal 

 fin communicates in the region of the trunk in Gad its with the dorsal l)ranch 

 of every spinal nerve (Stannius, 1849, 199, Taf. iv. fig. '±) — a significant fact 

 which is very helpful in determining the morphology of the accessory lateral 

 nerves. 



* Til many specimens of G. morrJma that 1 distected the glossoi)haiyngeus arose immediately ventral (Did anterior 

 to tlic loot of the lateralis. This it does in some other Teleo.sts. In the sections of G. virens, however, it arose 

 liebiiid the lateralis and between it and the vagus, which is its normal origin. 



