476 REIGHARD—PHELPS. [Vou. XIX. 
The single layer of cubical cells making up the posterior part 
of the dorsal wall of the foregut gives place to high columnar 
cells in the walls of the adhesive organ fundaments. The pro- 
toplasm of the peripheral end of each of these cells has em- 
bedded in it large conspicuous yolk granules and the nucleus 
with its prominent nucleoli also lies here, while the central 
end is largely composed of mucus (?) surrounded by a thin 
layer of protoplasm (Fig. B). 
The planes passing through the long curved axis of the 
two adhesive organ fundaments are not coincident with each 
other, and if projected would intersect behind the optic vesicles 
at an acute angle. The space between these fundaments on 
the one hand and the forebrain and foregut on the other 
hand is wedge-shaped and filled with loose mesenchyme. The 
fundaments of the adhesive organ are in close contact with 
the ectoderm, without intervening mesenchyme. 
The relations of the diverticula and foregut are shown in 
diagram in Fig. D. 
Fic. D.—Diagram of the foregut and its diverticula seen from the dorsal 
side in the stage shown in Plate, Fig. 2. The paired diverticula 
(adhesive organ) are shown displaced backward. The broken line 
indicates cavities: a, that of the button; b, that of the adhesive or- 
gan fundaments. The solid lines indicate outer surfaces; c, that of 
the adhesive organ; d, that of the button; e, the stomodaeum. The 
line composed of dots and dashes shows the posterior limit of the 
ventral wall of the foregut. 
b. The Mesoblast. In the preceding stage the mesoblast 
sheets of the head, when traced forward, were found to be- 
come narrower and to end just in front of the optic vesicles. 
In the present stage the mesoblast extends forward at the 
sides of the adhesive organ and in front of the stomo- 
daeum where it is continuous across the middle line. 
