FIG. 51. SAGITTAL SECTION OF AN EMBRYO CHICK OF 82 HOURS. 

 (After Duval.) 



A I, allantois. Ant, amnion. Ao, aorta. B, spinal canal BP, lung. C\ 

 bulbus arteriosus. C 2 , ventricle. C\ auncle. Cam, bottom of head-fold. Ch 

 notochord. Of, wall of neural tube, CF, cerebellum. G7>, pineal gland. HP 

 hypophvsis. I A, posterior end of fore-gut. IP, hind-gut. MA, rudiment of 

 wing. Ma, mesoblast of allantois. PC, pericardium. Ph, pharynx PP, body 

 cavity F 1 F 2 and F 3 , fore-, mid-, and hind-brain. VB, liver. VH, cerebral 

 hemisphere. VJ, umbilical wall. VOM, vitelline vein, xx, place of interruption 

 of section, part of the dorsal region being omitted. 



153 



