EH 



BH 



EV 

 TP 



VIII 



BR 



Ef 



BR.2 



AF 



BP 



Gl 



FIG. 3<DA. Transverse section through the head of a 12 mm. tad- 

 pole ; the section passing through the auditory organs, the pharynx and 

 opercular gills, the glottis and laryngeal chamber, and the heart, x 40. 



A, aorta; AF, afferent blood-vessel of second branchial arch; BH, 

 hind brain ; BR.i, .2, .3, .4, first, second, third, and fourth branchial 

 arches ; CH, notochord ; CP, pericardial cavity ; EA, anterior vertical 

 semicircular canal ; EF, efferent blood-vessel of second branchial arch ; 

 EH, horizontal, semicircular canal ; ER, recessus vestibuli ; EV, vesti- 

 bule of ear; QI, opercular gills ; HC.2, second branchial cleft; LC, 

 laryngeal chamber ; LT, glottis ; LY, lymphatic space ; OP, opercular 

 cavity; RA, auricle of heart; RV, ventricle ; TP, pharynx; v. 4, fourth 

 ventricle; x', choroid plexus of fourth ventricle; vin, auditory nerve. 



To face p. 1 29. 



