270 THE DEVELOPMENT OF THE CHICK 



During the fourth and fifth days the nerve grows back above 

 the roof of the pharynx, then turns ventrally behind the last 

 visceral pouch and forward in the floor of the pharynx. 



According to Chiarugi minute ganglia are formed in the second, 

 third, and fourth somites: but they soon degenerate (fourth day) without 

 forming nerves. 



Note: The structure called "hypophysis" on p. 249, sometimes called 

 Rathke's pouch, forms only the anterior lobe or glandular part of the hy- 

 pophysis of adult anatomy; the posterior lobe of the hypophysis is derived 

 from the structure called " saccus infundibuli " in this chapter, which is a deri- 

 vation of the floor of the brain. 



