No. 



.] THE CRANIAL NERVES OF AMPHIBIA. 129 



branch. This branch is probably the representative of the 

 R. auricularis VII in the frog (17). 



The latter of these two branches, i.e., the outer (mand. ex. b) 

 soon divides. The upper (dorsal) of these two subdivisions 

 (mand. ex. b^ gives off twigs, containing the smaller fibres, to 

 the skin. The bulk of the remainder, consisting of coarse 

 fibres, proceeds caudad, supplying a line of lateral sense organs 

 along the side of the head ventrad to those under the eye. The 

 larger ventral subdivision (mand. ex b^ proceeds caudad, par- 

 allel with the other, apparently supplying no lateral sense 

 organs until the dorsal subdivision has terminated. It also 

 appears to gradually lose its finer fibres. It divides at 585. 

 One part, proceeding caudad and dorsad, supplies lateral sense 

 organs with its coarse fibres. The other part proceeds caudad 

 and ventrad to about 800, where it bends mesad, proceeds 

 transversely across the ventral aspect of the body, and proba- 

 bly supplies a line of lateral sense organs present in this region. 

 There is, in addition to these branches of the R. mandibularis 

 externus, a small branch (mand. ex. c) which proceeds cephalad, 

 turning ventrad and caudad, as indicated in the chart. 



The dorsal of the three principal divisions of the R. hyoman- 

 dibularis divides. The ventral of these two divisions contains 

 nearly all the remaining fibres of VII ab, and soon enters 

 (357-346) the two muscles lying just mesad of the nerve. A 

 few of the coarse fibres of VII ab remaining with the dorsal 

 (fasciculus communis) division separate and also enter these 

 muscles. Of these two muscles, one is identified as repre- 

 senting the Mm. suspensorio-angularis and quadrato-angularis 

 described by Schulze (54). It appears to be one muscle here, 

 though there are some evidences of a separation into two. 

 The other muscle is the cerato-hyo-angularis of Schulze. 

 The behavior of these two sharply contrasted bundles of fibres 

 (VII aa and VII ab) and the manner in which the coarse ones 

 are, as it were, picked out to innervate the muscles, is very 

 interesting and instructive. The remainder of the dorsal 

 division of the R. hyomandibularis consists now of a bundle of 

 fine, lightly-staining fibres, among which are a number of deeply- 

 stained but small fibres. By tracing it out we have seen that 



