ER^ 



Fig. 22. — Horizontal section of a iadpole at the time 

 OF HATCHING. (After Marshall.) 



AFy afEerent branchial vessel of the first branchial arch. B F^ fore-brain. 

 BRX^ B R.%^ BH.S^ first, second, and third branchial arches. C, body-cavity or 

 coslom, F Ff efferent branchial vessel of first branchial arch. /^TJ/, nyomandi- 

 bular gill-pouch. // K, hyoi4arc_h. /A^, infundibulum. KA^ archinephric duct 

 of right side, KA ', archinephric duct of left side, seen in section. JCP, head- 

 kidney or pronephros. A* 5", third nephrostome of right head-kidney. A'^'^ same 

 of left side, seen in section. O F^^ olfactory pit. OSy optic stalk. TP^ pharyn- 

 geal region of mesenteron, 7"/, intestinal region of mesenteron, K, yolk-cells. 



59 



