The Development of the Frog 47 



before the stomodaeum. Before the neural 

 canal has been completely closed a small de- 



FiG. 17. — Longitudinal vertical section through the an- 

 terior END OF a tadpole SHORTLY AFTER THE TIME OF HATCHING. 



Length of the tadpole, 8 mm. (After Marshall.) 



A, auricle of heart. B /^, fore-brain. BH, liind-brain. B M^ mid-brain. 

 C\ pericardial cavity. CK, vesicle of cerebral hemispheres. /, infundibulum. 

 Z, liver, JV^ notochord. O, depression of floor of fore-brain from which the 

 optic vesicles arise. t7jE, oesophagus. /', pituitary body. /'iV", pineal body. 

 6*, central canal of spinal chord. SI?^ stomodaeum. 7\ truncus arteriosus. K, 

 ventricle. i\ yolk-cells. 



pression is seen below the blastopore (Fig. 1 2, 

 PD) ; this is the beginning of the anal in- 

 vagination. At the same time a diverticulum 



