THE HYPOPHYSIS CEREBRI 



455 



mordium of both the hypophysis itself and the naso-pharyngeal 

 canal, the dorsal part giving rise to the glandular lobe of the 

 pituitary body. 



Pisces. — (i) Elasmobranchii. — The pituitary body in Elas- 

 mobranchs has been described by Stendell (19), Herring 

 (7 and 8), Baumgartner and others. Herring (8) states that the 

 " elasmobranch pituitary differs from all other pituitaries in 

 not possessing a posterior lobe. The brain wall of the embryo 

 merely evaginates to form a paired saccus vasculosus, but no 

 pars nervosa is formed." On the other hand, Stendell (19) 



T/C A.CQTV 



Fig. 2. 



describes and figures a well-developed, branched " Hirnteil " 

 in the Notidanidae. 



The third ventricle in Elasmobranchs (fig. 2) is produced 

 backwards and downwards into an infundibular recess (I. R.), 

 the dorsal wall of which is evaginated and richly vascularised 

 and forms the saccus vasculosus. Its ventral wall may 

 remain thin, as in Scyllium, or may be produced into 

 branching processes, solid as in Acanthias, or hollow as in 

 Heptanchus, which constitute the nervous lobe of the pituitary. 

 This is invested by an epithelial pars infundibularis (P.I.)* 



The pars buccalis as a whole is divisible into an anterior 

 lobe, superior (or dorsal) lobes, and inferior (or ventral) lobes. 

 The anterior lobe in Scyllium, Raja, and Acanthias forms a 



