20 



SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. 54 



Fig. 6a. A sagittal section through the hypophysal region of the same 

 embryo. Objective ^ inch ; ocular 2 inch. 



Fig. 7. A sagittal section through the hypophysal region of a 13 cm. embryo. 

 Objective ^ inch; ocular 2 inch. 



Lettering. 



b. v., blood vessel. 



c, cerebral hemispheres. 

 cb., cerebellum. 



ch., notochord. 



c. p., choroid plexus. 



e., eustachian valve. 



/. b., fore-brain. 



h., hypophysis. 



h. b., hind-brain. 



ht., heart. 



h. s., hypophysal stalk. 



in., infundibulum. 



in'., infundibular pit. 



/., slit-like lumen of hypophysis. 



in. b., mid-brain. 

 md., mandible. 

 n., nasal cavity. 



o.-o'"., lateral diverticula of hypophy- 

 sis. 

 p., paraphysis. 

 p. a., paraphysal arch. 

 p. c, posterior commissure. 

 ph., pharynx. 

 p. n., posterior nares. 

 p. s., pharyngeal sac. 

 v., velum. 



v.a., post-velar arch (dorsal sac). 

 vs., velar vesicles. 



