l^iS ME. F. J. COLE ON THE .STEUCTUEE AND MOEPllOLOGY OF 



connects the Vllth and IXtli nerves is homologous throughout the different classes of 

 vertebrates there can be little doubt. It is further certain that this nerve is a branch 

 of the glossopharyngeal, is primarily quite distinct from the facial, and in the adult 

 only accompanies a branch of the latter nerve. It is the main body of the first, visceral, 

 palatine, or pharyngeal branch of the IXtli, and as sucli, in the lower vertebrates at any 

 rate, belongs to the fasciculus communis system, and consists very largely, if not entirely, 

 of visceral sensory fibres. It passes forwards, and, as a general rule, becomes related to 

 the palatinus facialis, and either accompanies the main trunk of the latter or some of 

 its branches, or it may completely fuse with it. It is hence usually not an anastomosis 

 at all, in the sense that an anastomosis should l)e a perfect mingling of two nerves. 

 Its forward continuation to the trigeminus, described by Van Wijhe and Pollard, I am 

 inclined to view with some doubt, and await further details on the point. The difficulty 

 in the case of the trigeminus is that the visceral sensory branch is typically unrepresented 

 in this nerve (cp. Goronowitsch, 1888, 89), and the anastomosis could not, therefore, as 

 Van Wijhe describes, be connected with its " palatine " branch. The explanation of an 

 anastomosis at all is to be sought for in the fact that both nerves concerned have a 

 similar peripheral distribution, and may hence fitly accompany one another. The 

 interpolation of the auditory organ has doubtless assisted in further separating the 

 nerves, and thus converting a simple fact into a phenomenon. 



L. The Metamekism of the Lateral line System. 



A description of the nerves supplying the lateral sense organs would naturally follow 

 the descri2)tion and discussion of the trigemino-facial ganglion and Jacobson's 

 anastomosis, but it is obvious, however, that before this can be attempted it is expedient 

 to enquire into the morphological value of these nerves, to determine to which of the 

 cranial nerves, if any, they belong, and in fact to consider the whole question of the 

 metamerism of the lateral sense organs. The structure and development of the lateral 

 sense organs show conclusively that they were originally confined to the head, and have 

 only secondarily been continued on to the trunk. How did they arise ? Are they 

 segmental at all, and if so is the segmentation primitive or acquired ? It is perhaps 

 unnecessary for me to point out that these questions can only be solved satisfactorily by 

 determining the morphology of the nerves supplying them. It is indeed true that the 

 position of the organs themselves and the relation they have to the dermal bones of 

 the skull may in some Avay help us, but their position and structural relations are too 

 variable, and tlieir significance too equivocal, to have anything more than confirmatory 

 importance attached to them. We thus have to review the facts of development and 

 adult structure and to ascertain in what direction modern research is leading us. 



Eisig (18S7, 65), whose work will also be discussed elsewhere, naturally considers the 

 lateral line organs metameric, and in fact goes so far as to consider the probability of 

 their being once connected with spinal nerves. This he endeavours to establish by 

 referring to the Avork of Julin and Ransom and Thompson on the Lamprey. These 

 authors, however, were dealing with the so-called lateralis nerve of Petromyzon, and as I 

 shall show later on that this is 7iot a lateral line nerve at all, Eisig's contentious must 



