976 MRS. O. A. MEURITX HAWKES ON THE [DeC. 11, 



divides into two rami. One of these (K.. H.) passes to the inter- 

 mandibular muscles. It was not possible to determine satisfactorily 

 if any cutaneous fibres were present. This nerve is the ramus 

 hj^oideus. The second ramus passes inwards and forwards to be 

 distributed to the floor of the mouth, in front of and at the sides 

 of the tongue ; presumably this consists of communis fibres, and 

 is therefore the r. internus mandibularis. 



Two nerves originate side by side from the geniculate ganglion, 

 the cephalad being about twice the size of the caudad. The 

 former is the r. pre-trematicus facialis ; the latter the remnant 

 of the r. post-trematicus facialis, 



(d) The r. post-trematicus YII. (Pt.F.) passes somewhat back- 

 ward, and at a distance of 5 mm. from its origin sends a fine 

 branch jjosteriorl}'' to be distributed to the top of the spiracle. 

 At a further distance of 5 mm. three branches originate — two of 

 these pass along the top and to the caudad side of the spiracle, 

 whilst the third passes inwards and anteriorly to supply tissues 

 of the upper jaw. The remainder of this r. post-trematicus then 

 bends suddenly cephalad to unite with the r.. pre-trematic VII. 

 This ramus pi'obably I'epi'esents the original position of the com- 

 plete r. post-trematicus YII., part of whose fibi'es are now united 

 with lateralis elements to make up the t. hyomandibularis. The 

 small size of this ramus is due to the disappeai'ance of the spiracular 

 gill and the reduction of the spiracle, which, in this species, is 

 merely a pouch opening into the hyobranchial cleft. Like other 

 degenerating nerves, it has a tendency to coalesce with neighbour- 

 ing ?aerves : thus, here it joins the r. pre-trematicus, whilst in 

 other cases it has coalesced with the r. mandibularis V. (13. p. 413). 

 In a second specimen the post-trematicus divided into seven fine 

 branches which had no connection with the pre-trematic ramus. 



(e) The r. pre-trematicus VII. passes cephalad and downward, 

 giving off three fine branches (fig. 1) which can be traced for only 

 1 cm. towards the snout into the connective tissues. Aftei' the 

 luiion of pre- and j)ost-trematic rami the two palatine branches 

 (fig. 1, P.) are given oft", and then the nerve continues its course as 

 the chorda tympani (Pr.F. (ch.)). 



(/) The rami palatini YII. pass cephalad on to the mucosa of 

 the mouth, running parallel to one another, the one near the 

 median line, the other more laterad. 



{g) The chorda tympani, which is a direct continuation of the 

 r. pre-trematicus, passes caudad and ventrad, immediately under 

 the mucosa of the anterior wall of the first gill-cleft — that is, it 

 passes along the upper jaw between the latter and the hyoid arch. 

 The chorda was traced on to the ventral part of the mouth. On 

 the way it gave ofi' blanches to the hyoid mucosa and a few to 

 accompany the cartilages of the mandibular arch. This nerve 

 fulfils every r-equisite for the chorda as determined by Cole 

 (3. p. 657 on), viz. : — (1) in arising from the base of the r. 

 palatinus; (2) in entering into branchial relations with the 

 mandibular axch ; (3) in consisting of special sensory fibres ; (4) in 



