BOWERS. — CRANIAL NERVES OF SPELERPES BILINEATUS. 187 



and soon divides into two nearly equal branches, both of which first run 

 ventrad into the lower jaw, then cephalad, nearly parallel to each other, 

 to the tip of the chin, supplying the lateral-line organs along their 

 course. One of these ( VII. md. ex.') is more ventral and median than 

 the other ( VII. md. ex.). Strong ('95, p. 134) says of this branch in 

 Amblystoma : " It is a cutaneous nerve ; and probably, as in the tad- 

 pole, supplies the lateral sense organs." Its ganglion is " composed of 

 large ganglion cells." Herrick ('94, p. 199), however, found no gan- 

 glion in the course of the r. mandibularis externus in Amblystoma. 



Strong ('95, p. 163) has called attention to the fact that the r. buc- 

 calis of von Plessen und Rabinovicz is misnamed, that it corresponds to 

 r. mandibularis externus VII., and is derived from the ventral division of 

 the lateral [i. e. lateral-line] root. Apparently a further interpretation 

 of their designations must be made, for their " Begleiter des R. hyoideo- 

 mandibularis " (their ramus hyoideo-mandibularis and by inference 

 its " Begleiter" are distributed to the skin of the cheek and the lower 

 jaw) also clearly belongs to the lateral-line component. It is probable 

 that, while their r. buccalis corresponds to one of the two branches (the 

 more lateral, VII. md. ex.) of r. mandibularis externus VII. as found in 

 Spelerpes, their "Begleiter" corresponds to the other (the more nearly 

 median, VII. md. ex.') branch. 



Herrick ('94, p. 199), following too closely von Plessen und Rabin- 

 ovicz, has repeated for Amblystoma their mistake concerning this " Be- 

 gleiter." He describes the ramus buccalis and the accessory ramus 

 hyomandibularis ("Begleiter") as following the ectal aspect of the jaw 

 bone to the tip of the lower jaw, and as being distributed to the skin. He 

 says : "The fibres of the ramus buccalis are mainly, if not wholly, derived 

 from the dorsal root, as Strong has pointed out. The nerve which I have 

 called the accessory hyomandibular seems to be the same as Strong's 'small 

 branch to lower jaw,' which he derives from the fasciculus communis 

 and considers the representative of the chorda tympani of higher forms." 

 But obviously the homologue of Strong's " small branch to lower jaw " 

 is not Herrick's accessory hyomandibular, but his r. alveolaris. 



(g.) R. hyomandibularis VII. in Spelerpes is very short, as com- 

 pared with its length in the tadpole. In the latter, it is prolonged, as it 

 were, almost to the anterior margin of the eye before its first branch, r. 

 hyoideus VII., is given off. The condition in Spelerpes corresponds 

 more nearly to that in the adult frog. Presumably the 23 mm. larva 

 of Spelerpes undergoes much less alteration in the course of its further 

 development than does the tadpole, so that the two stages are not 



