166 OUTLINES OF CHORDATE DEVELOPMENT 



ep 



B 



bh 



ht 





FIG. 58. Diagrams of median sagittal sections of the anterior ends of frog 

 larvae. After Marshall. A. Of a larva just before the .opening of the mouth. 

 B. Of a 12 mm. larva (at the appearance of the hind-limb buds), a, Auricle; 

 ao, dorsal aorta; 6, gall bladder; bh, basihyal cartilage; ch, cavity of cerebral 

 hemisphere (lateral ventricle); e, epithelial plug closing the oesophagus; ep, 

 epiphysis; g, glottis; h, hypophysis; H, hind-brain; hr, cerebral hemisphere; ht, 

 horny "teeth"; hv, hepatic vein; i, intestine; if, infundibulum; j, lower jaw; 

 I, liver; ly, laryngeal chamber; m, mouth; M, mid-brain; mb, oral membrane (oral 

 septum); n, notochord; o, median portion of opercular cavity; oe, oesophagus; 

 p, pharynx; pb, pineal body; pc, pericardial cavity; pd, pronephric (mesonephric) 

 duct; pt, pituitary body; pv, pulmonary vein; pill, choroid plexus of third ven- 

 tricle; pIV, choroid plexus of fourth ventricle; r, rostral cartilage; ro, optic recess; 

 s, stomodseum; sv, sinus venosus; t, thyroid body; ta, truncus arteriosus; tp, tuber- 

 culum posterius; v, ventricle; vc, inferior (posterior) vena cava. 



