Figure 16_g_ represents a sagittal section of the anterior half of the body of an embryo of this or possibly a slightly younger stage of development. The three regions of the brain are clearly indicated, as well as the cavity of the spinal cord (_sc_). The roof of the hindbrain has been made too thick in the figure; it should be represented by a mere line. A little mesoblast is to be seen at places between the roof of the brain and the superficial ectoderm. A slight invagination of the epithelium (_p_), between the floor of the brain and the anterior end of the notochord, probably represents the beginning of the hypophysis. No indication of the paraphysis is yet to be seen. Extending from the region of the hypophysis to the posterior end of the section is the notochord (_nt_); it is much vacuolated and gradually increases in thickness toward the posterior, though its outline is quite irregular; except at the extreme anterior end and at one or two other places, it lies in close contact with the floor of the neural tube. Directly under the notochord lies, in the posterior half of the figure, the large dorsal aorta (_ao_). The pharynx (_ph_), opening between the end of the forebrain and the thick mandibular fold (across which opening the amnion, _a_, of course extends), is a funnel-shaped space which passes out of the plane of the section toward the posterior end of the figure. Its thick endodermal lining extends to the mandibular fold on the ventral side, while on the dorsal side it gradually thins out and becomes continuous with the thin ectoderm that extends over the forebrain. Just back of the mandibular fold is the bulbus (_b_), and back of that is the edge of the ventricle (_vn_). Posterior and dorsal to the ventricle the liver (_li_) is seen as an irregular mass of cells, and dorsal to the liver one of the Wolffian bodies (_wt_) is cut through its extreme edge. STAGE XIV FIGURES 17-17_g_ (PLATES XXIII., XXIV.) Body flexure has increased until now the forebrain and tail are almost in contact (Fig. 17). The eye has developed somewhat; the ear vesicle, which is not shown in the figure, is small and seems to lie nearer the ventral side; the nasal pit is much larger and is crescentic in shape. The hyomandibular cleft (_g′_) still persists as a small crescentic slit, while the next three clefts are now represented merely by superficial grooves separated by distinct ridges, the visceral folds. No indication of a fifth cleft is seen. The maxillary process (_mx_) grows ventralward under the forebrain and is already longer than the mandibular arch (_md_).