188 PROCEEDINGS OF THE AMERICAN ACADEMY. 



directly comparable. Evidently the name r. hyomandibularis must be 

 restricted in Spelerpes to the short trunk of the ventral part of the 

 seventh, which is included between the region of its separation from the 

 eighth and that of the giving off of r. hyoideus. Though much shorter 

 than in the tadpole, it is made up of the same components, except that 

 it does not embrace the general cutaneous. This constituent is repre- 

 sented exclusively by the communicating branch from IX. to VII. 

 Since in Spelerpes this r. communicans IX. ad VII. is not received by 

 the hyoraandibular trunk of seven, but by r. hyoideus after its separa- 

 tion from the trunk (Fig. 2), it is probable * that no general cuta- 

 neous fibres are included in the hyomandibularis proper. This, however, 

 is not a fundamental difference, being merely a question of the earlier 

 or later accession of r. communicans to branches of the seventh. In 

 one point, only, is a greater importance to be noted : r. mandibularis 

 ext. in Spelerpes probably does not contain, as in the tadpole, a general 

 cutaneous component. 



The (h) r. hyoideus after receiving r. communicans from IX. + X, 

 curves latero-ventrad and is distributed to m. digastricus and m. mylo- 

 hyoideus posterior and to the skin ventral to them. The main branch 

 (VII. hoi.) is figured in neutral tint, since the proportion of the two 

 components was not accurately ascertained. 



F. Glossopharyxgeus AND Vagus. 



1. Roots. — The roots of this group, like those of the seventh and 

 eighth, show apparently a close correspondence to the condition in 

 Necturus, though a careful comparison will be necessary to determine 

 this with certainty. The most cephalic and most dorsal root is the 

 lateral-line component (PI. 1, Figs. 1, 2, /X.'"*"^) ; it resembles dorsal 

 VII. in appearance and position. In this case, however, the root is 

 composed of two bundles. It is equivalent to Kingsbury's IX.^'^^ and 

 to Strong's first root of IX. +X. 



The second root (IX.^+*) emerges one section (20 ^ thick) caudad 

 and slightly ventrad of the first root; it is composed of (1) the char- 

 acteristic fine colorless fibres of the fasciculus-communis component and 

 (2) a ventral bundle, presumably motor. It corresponds to Kingsbury's 

 IX. ^+* and to Strong's second root. 



The third root {X.^), the equivalent of Kingsbury's X.^, emerges 



* It is of course possible (?) that some fibres from the r. communicans take a 

 centripetal course in the r. hyoideus and thus reach the liyomandibular trunk of 

 VII. 



