402 Journal of Comparative Neurology. 



with the same nerves. The cases all have this in com- 

 mon, that they are related centrally to the communis 

 system of nerves and peripherally supply the meninges 

 and skin of the top of the head and of the trunk. It 

 appears from the descriptions of Merkel ('80), Leydig 

 ('94), Harrison ('95), Allis ('97) and others that the cuta- 

 neous distribution is mainly, if not wholly, to terminal 

 buds. 



The relations to the vagus system are most various. In 

 most, if not all, of these cases it is clear that communis 

 fibres with essentially the same distribution go out with 

 the IX or X nerves or both and the anastomosis of these 

 two sets of fibres is easily explicable. Since the branches 

 which go into the body supply in some of the cases ter- 

 minal buds in the same regions as the lateral line organs 

 supplied by the r. lateralis vagi, the more or less inti- 

 mate anastomosis with the latter nerve is also easy of 

 comprehension. 



Phylogenetic speculations are, perhaps, premature, yet 

 from the evidence now in hand I incline to the belief that 

 the peripheral anastomosis is the more primitive. As 

 terminal buds migrated into the trunk from the head, 

 communis fibres seem to have accompanied them from 

 both the VII and IX roots and probably also the vagus. 

 These nerves effected sub-cutaneous anastomoses with 

 each other and probably with similar fibres accom- 

 panying the r. lateralis vagi. Menidia, then, is probably 

 very near the primitive type. As the recurrent systems 

 increased in importance, two lines of differentiation were 

 followed. On the one hand, the facialis portion was 

 exaggerated at the expense of the post-auditory portion 

 and we have forms like the siluroids with enormous r. re- 

 currens VII with no considerable vagal participation. In 



