s 



186 PROCEEDINGS OF THE AMERICAN ACADEMY. 



it extends farther anterior than the latter, (c) The acusticus. Three of 

 the branches of the eighth nerve have been represented in the drawings 

 in neutral tint, — ramulus ampullae anterioris (rml. amp. «.), ramulus 

 ampullae externae {rml. amp. ex.), and ramulus ampullae posterioris 

 (?•/«/. amp. p.). These were plotted simply to show their relation 

 to the seventh nerve. Fibres to the macula ac. sacculi and macula 

 ac. neglecta were observed, but these were only slightly differentiated 

 at the stage here reproduced. They could be clearly traced in a larva 

 40 mm. long. The 'anterior portions of VII. and VIII. remain con- 

 nected with each other until after r. palatinus VII. is given off; the 

 acoustic then curves dorsad and enters the ear capsule, while the faci- 

 alis curving ventrad and ectad passes out through the cartilage of the 

 skull. 



The first of the branches to be given off from the ventral part of the 

 facialis is the (d) r. palatinus, whose fibres are derived exclusively from 

 the fasciculus-communis component. The ganglion of this root, lying close 

 to the point where r. palatinus emerges, is fused with that of the eighth 

 nerve and "represents probably the geniculate ganglion " (Kingsbury, '95, 

 p. 187), The fibres of this component are always easily recognizable, 

 since they are very fine and with iron haematoxylin take only a faint 

 stain, or sometimes none at all. The greater portion of the fibres of the 

 fasciculus communis goes to form this branch (r. palatinus), which passes 

 directly cephalad, giving a few fine branches to the roof of the pharynx, 

 and anastomosing, as already stated, with r. ophthalmicus V. 



The few remaining fibres of the fasciculus communis pass out through 

 the ventral wall of the ear capsule with the hyomandibular portion of the 

 facialis, run thi'ough the ganglion of the lateral-line component of 

 the facialis, which lies beneath the cephalic end of the otic capsule, and 

 emerge as (e) r. mandihularis internus VII. ( VII. md. {.), or r. ulveolaris 

 VII., which Strong ('95, p. 187) homologizes with the chorda tympani 

 of higher vertebrates. In Spelerpes this branch is very minute, and in 

 the sagittal sections used for reconstruction could be traced only a short 

 distance anterior to the articulation of the jaw (Figs. 1, 2); but in trans- 

 verse sections it could be traced along the inside of the jaw to its termi- 

 nation in the ventro-lateral wall of the pharynx. It does not, in any 

 part of its course, enter a canal, agreeing in this respect with Siren la- 

 certina as described by Wilder ('91). 



(/".) R. mandibidaris externus VII. {VII. md. ex.), or r. meiitalis VII., 

 the ventral part of the lateral-line component of the seventh, passes ven- 

 trad and cephalad from its ganglion, which lies under the otic capsule, 



