26o Journal of Comparative Neurology. 



Caecilians (Waldschmidt, '^7). In these forms certain twigs 

 of the r. maxillaris seem to fuse with twigs of the r. ophthal- 

 micus profundus ; but it is impossible to interpret this condition 

 until the composition of these twigs is known. In none of 

 these forms have the observers differentiated the lateralis from 

 the general cutaneous fibers. 



Herrick ('99) describes, in Menidia, a nerve ("/<?, 2") 

 which is given off from the truncus infra-orbitalis at the poste- 

 rior level of the eye, and the general cutaneous part of which 

 he says "corresponds in nature and position rather closely to 

 the most lateral one of the accessory trigeminal branches in the 

 tadpole of the frog." Also, in Amia (Allis, '97, p. 605), in 

 Chimaera (Cole, '96, p. 649) and in Gadus (Cole, '98, p. 159; 

 Herrick, 1900, p. 280), homologues of one or more of the 

 "accessory" rami of the trigeminus in the tadpole have been 

 recognized. These proposed homologies introduce a question 

 concerning the morphology of these accessory nerves which 

 was not discussed in my earlier communication : i. e. if the so- 

 called r. maxillaris of Amblystoma is not homologous with that 

 of Rana, which of these nerves represents the r. maxillaris of 

 fishes ? 



If the "accessory" ramus of the tadpole is represented in 

 fishes by small branches of the t. infra-orbitalis as Allis, Cole 

 and Herrick maintain, and if it is represented in the Ambly- 

 stoma by the entire general cutaneous component of the infra- 

 orbital trunk, then there can be no r. maxillaris of the piscine 

 type in Amblystoma. On^ this hypothesis, also t he r. maxil- 

 laris of fishes would become the equivalent of the r. maxillaris 

 of Rana. However, though my conclusions concerning the 

 amphibian nerves may introduce new questions of interpreta- 

 tion, they do not seem to me to increase the difficulties. On 

 the other hand, they seem to elucidate the main question at 

 issue, which is to explain the differences in the so-called r. 

 maxillaris as it appears in the three types, Urodela, Anura and 

 fishes. 



In the consideration of this question one well known fact 

 should be emphasized : the r. maxillaris of Rana is anatomically 



