

§d0^ 



Fig. 51. — Sagittal section of an embryo chick of 82 hours. 

 (After Duval.) 



Ai, allantois. Af", amnion. Ao, aorta. B, spinal canal, BP, lung. C^, 

 bulbus arteriosus. C, ventricle. C^, auricle. Cam, bottom of head-fola. C/z, 

 notochord. O/, wall of neural tube, Cf^, cerebellum. C/*, pineal gland. ///", 

 hypophysis, lA^ posterior end of fore-gut. //*, hind-gut. MA^ rudiment of 

 wing. Jkfn, mesoblast of allantois. PC^ pericardium. /'^, pharynx. PP^ body 

 cavity, y^. V^, and F^, fore-, mid-, andhind-brain. VB^ liver. VH, cerebral 

 hemisphere, fy, umbilical wall. VOM. vitelline vein, jtjt, place of interruption 

 of section, part of the dorsal region being omitted. 



153 



