DEVELOPMENT OF THE HYPOPHYSIS 437 
Fig. 38 Transverse section of the superior lobe of a95 mm. embryo. (H.E.C. 
Series 1882). x 450. 
Fig. 39 Sagittal section of the superior lobe of the hypophysis of a pup 
showing one of the cell columns and a portion of the roof. > 400. 
non-granular. Fewer mitotic figures are to be found at this 
time. In the pup the roof is a little thicker than in the pre- 
ceding stage. Above the roof there are many cell columns which 
are outgrowths from the roof proper (fig. 39). The relations: of 
cell columns and roof to each other are shown in figure 39. The 
roof has a narrow outer zone of granular cytoplasm. Its nuclei 
are oval and have a light chromatin network. The cell columns 
come into close contact with the overlying floor of the vascular 
sac (fig. 39). Numerous capillaries and a loose connective 
tissue fill the spaces between the cell columns and between the 
roof of the hypophysis and the floor of the vascular sac. The 
columns have an outer, granular cytoplasmic zone. ‘The cells 
are acidophilic. The nuclei are spherical in outline, have a 
light chromatin network and usually one or two larger chromatin 
masses or nucleoli. 
Only a brief statement can be given at this time concerning 
the development of the glandular columns of the superior lobe. 
In the region of the superior lobe in all embryos up to the 50 mm. 
stage, the nuclei are elongate-oval in outline and are arranged 
in two or three layers (fig. 36). In a 50 mm. embryo some of 
the nuclei at the periphery are spherical (fig. 37). It is possible 
