BOWERS. — CRANIAL NERVES OF SPELERPES BIUNEATUS. 189 



at some distance caudad of the preceding and is made up of three com- 

 ponents: (1) most dorsal, fine fasciculus-communis fibres, (2) more 

 ventral and caudad of fasc. com. a large bundle of coarser fibres (ascend- 

 ing X.), which correspond to those of ascending V., and (3), in this 

 differing from Necturus, a ventral bundle (motor ?). The third root 

 in the tadpole has, according to Strong, the same triple composition, but 

 in that animal the fasciculus-communis fibres emerge ventral to those of 

 ascending V., not cephalad of them, as in Spelerpes. 



The remaining: four roots are small and could not be traced in the 

 sagittal series of the 23 mm. larva ; but they were plotted on the 

 frontal reconstruction (Fig. 2) from frontal sections of another 23 mm. 

 specimen, and the results were checked by the study of other series 

 of (transverse) sections. These four roots all appear to be motor, for 

 they arise in the same horizontal plane from ventral fibres, which turn 

 cephalad after emerging from the medulla. Kingsbury's X.'^, X.^, 

 and X.^ are in his opinion motor, but he says that X* is probably 

 sensory, and that its fibres accompany those of ascending V. 



2. Branches. — The coarse fibres of the first root in Spelerpes can be 

 easily traced through the upper part of the ganglion IX.+X., and all 

 but a few of them, which are given off dorsally (see Fig. 1, rm. su'tp.), 

 pass out at the posterior end of the ganglion as the lateral-line nerves — 

 (a) ramus lateralis — to be distributed to the lateral-line sense organs of 

 the body. 



The remaining coarse fibres form a branch (rm. sii'tp.) which passes 

 dorsad and ectad and divides into two small branches which innervate 

 sense organs just posterior to the ear. Following Strong's nomenclature, 

 this may be called (b) ramus supratemporalis., though it does not curve 

 cephalad, as in the tadpole. It may be noted in passing that the " ectad 

 tendency" of the cranial nerves in Spelerpes, as compared with the 

 " cephalad tendency " in the tadpole, is a noticeable difference between 

 the two forms, and is probably due to the more anterior position of the 

 gills in the tadpole. 



There is a bundle of general cutaneous fibres {rm. aur.), which leaves 

 ganglion IX.-|-X. in company with r. supratemporalis, from which, 

 however, it immediately separates and runs dorso-cephalad to the skin 

 above the ear capsule. It corresponds in composition and distribution 

 to the branch called by Strong (c) ramus auricularis, and known in the 

 frog as r. cutaneus dorsalis. 



From the cephalo-lateral portion of the ganglion there pass out three 

 branches, which for a short distance are united into a single trunk. The 



