SOUND-TRANSMITTING APPARATUS OF CAUDATA 



331 



cells which comes into close relation with the caudal side of the 

 hyomandibular cleft, a relation which is not lost until late larval 

 life. The ear capsule is clearly indicated by distinct and closely 



Fig. 2 Transection of the fenestral region of an embryo Spelerpes bislineatus 

 10 mm. long. A.c, arteria carotis interna; A.e., auditory epitheAium; Br., brain; 

 Ep., epidermis; H.c, hyomandibular cleft; O.c, oral cavity; O.ep., oral epi- 

 thelium; V.p.L, vena petrosolateralis. 



associated cells and the facial nerve and its branches may be 

 distinctly traced. 



In larvae which have reached a length of 15 mm. the columellar 

 cord of cells extends caudad to the cephalic part of the fenestral 

 membrane, against which it rests, but to which it is not closely 



