192 



HAROLD J. COOPER 



2). The organ belongs to the second class in Vincent's ('12) 

 grouping, possessing a solid nervous lobe, but an infundibular 

 cavity extending almost to it. 



Fig. 3 Midsagittal section of the hypophysis of a 12-mm. embryo (semi- 

 diagrammatic). /, infundibular cavity; PN, pars neuralis; PI, future pars 

 infundibularis; R, residual lumen; PG, future pars distalis; S, epithelial stalk; 

 OC, optic chiasma; BC, buccal cavity. X 35. 



B. MICROSCOPIC 



Since I have had but little embryological material, T can give 

 no details of the development. The only stage I have seen is 

 found in a 12-mm. embryo, a midsagittal section being shown in 

 figure 3. The hypophyseal pouch (Rathke's pouch) is just about 

 to be cut off at S. At this stage there has taken place no dif- 

 ferentiation of the glandular portion into distal and juxtaneural 

 lobes. 



