78 EDWARD PHELPS ALLIS, JR. 



fundi, with ramuli nasalis and frontalis, but no evident trace of 

 an ophthalmicus trigemini, excepting as it is represented in the 

 so-called ophthalmicus superficialis facialis; and this, with the 

 further absence of the ophthalmicus superficialis facialis, is 

 apparently the condition found in all higher vertebrates. 



Herrick ('09) says that' the facialis nerve of primitive verte- 

 brates was a branchiomeric nerve, supplying a gill-bearing seg- 

 ment and containing at least four components. It is not said 

 that one of these components was a general cutaneous one, but 

 that seems understood. In the mandibular arch similar condi- 

 tions must certainly have existed, and probably also in a pre- 

 mandibular arch supplied by the nervus profundus. In any 

 event, it is certain that the general cutaneous tissues of the region 

 innervated in Polypterus, Ceratodus, and the Selachii by the 

 nervus profundus are innervated, in the Holostei and Teleostei, 

 either by both the portio profundi and the ophthalmicus tri- 

 gemini, or by the latter nerve alone. There must then have 

 been, phylogenetically, either an actual change of innervation of 

 these tissues in one of these two groups of fishes or the tissues 

 innervated, in one of the groups, by one segmental nerve, must 

 have degenerated, with the related nerve, in the other group, 

 and there have been replaced by tissues primarily innervated 

 by the nerve of an adjacent segment. The presence, in Amia, 

 of a degenerate ramus ophthalmicus profundi would seem to 

 exclude the possibility of assuming that the remaining fibers of 

 the latter nerve have simply, in the Holostei and Teleostei, ac- 

 quired a different and more favorable course than that followed 

 by them in the Selachii. But however this may have been, it is 

 evident that, of the several fishes above considered, Polypterus, 

 the Dipneusti, and the Elasmobranchii alone present actual 

 conditions of these nerves that could have led to those found in 

 higher vertebrates, for that a nerve once so degenerated as the 

 ramus ophthalmicus profundi of the Holostei and Teleostei would 

 have been redeveloped and perpetuated seems improbable. 



Palais de Carnoles, Menton, France 

 August 26, 1918. 



