DEVELOPMENT OF THE HYPOPHYSIS 435 
Fig. 35 Sagittal section of a portion of the inferior lobe of the hypophysis of 
apup. X 400. 
as the inner, wider one, stains lightly in a 50 mm. embryo. In 
an 86 mm. embryo the outer zone has fine granules. The cells 
are slightly acidophilic. The nuclei are elongately oval in out- 
line as in the anterior lobe. In the pup many outpouchings 
indicate the beginning glandular development. The upper wall 
is three or four cell-layers thick (fig. 35). There is a wide, inner, 
clear-staining cytoplasmic zone. The outer narrower rim is 
slightly granular. The nuclei are oval in outline, as in the 
anterior lobe. Numerous densely staining chromatin masses 
are to be seen. The lower wall or floor is much thinner. It is 
composed of only one or two layers of cells and has a narrow, 
inner, cytoplasmic rim. This zone, as in the roof, stains very 
lightly and is non-granular. The outer rim is, however, quite 
granular. The nuclei are like those in the roof but contain a 
somewhat denser chromatin network. 
c. Supervor lobe. Ina21 mm. embryo the wall of the superior 
end of the hypophyseal anlage is thickest where the superior 
lobe later develops (fig. 36). The nuclei are large and oval and 
have a light chromatin network. In a 50 mm. embryo (fig. 37) 
the wall in this region is considerably thicker than in the 21 mm. 
embryo because of an increase in the number of cell layers. There 
