268 E. A. BAUMGARTNER 



stalk or pharyngeal roof, are present. The pharyngeal roof is 

 two-layered, having an inner columnar, and an outer flat epi- 

 thelial layer which, in the stalk, is replaced by a columnar layer 

 of cells. 



The nuclei of the hypophyseal wall, three to five rows deep, 

 are oval in a 14 mm. embryo (fig. 54). In the glandular out- 

 growths present at this stage, usually two, three, or even more 

 rows of round nuclei are found arranged about the clear, central 

 cytoplasm or occasional lumen. The nuclei about the original 

 hypophyseal lumen are basal in position so that a narrow cyto- 

 plasmic zone borders the cavity. Cell walls and the cuticular 

 border are indistinct, but the basal membrane is still prominent. 

 Mitotic figures border the lumen in all the stages described. 

 The one or two spherical nucleoli are relatively very large. 

 They are present also in the nuclei of the mesenchyma, epi- 

 thelium of the oral cavity, and the nerve cells. The stalk is 

 lighter staining than the hypophyseal epithelium and shows 

 signs of degeneration. 



The entire hypophysis in a 28 mm. Aromochelys embryo is 

 formed of solid cords of tubules with minute lumina. A very 

 small residual lumen is present in the pars intermedia. The 

 latter is formed of glandular cords, sometimes with enlarged 

 ends, radiating in all directions, except toward the infundibulum 

 (fig. 58). There are four or five rows of oval nuclei in these cords 

 and in the roof adjacent to the infundibulum. Near the caudal 

 end of the floor of the anterior lobe, a cystic tubule, the rem- 

 nant of the stalk, occurs in some specimens. It contains a 

 reticular substance and is lined by a single layer of columnar 

 cells. The other tubules of this part have very little cytoplasm 

 and three to five rows of nuclei. Sections of several cords of 

 the anterior lobe and the thin lateral buds are shown in figure 

 55. In the cords the nuclei are almost round and some are very 

 dark. Onfy occasionally does the cytoplasm of a cell show 

 beginning differentiated staining. In the much lighter staining 

 lateral buds (fig. 55) the nuclei are somewhat larger. All con- 

 tain a prominent nucleolus. The attachment of the lateral buds 

 to cords of the anterior lobe can be seen in some sections (fig. 8). 



