The earliest condition of the embryonic vascular system, as described by Wagner and other embryologists, consists of a venovascular chain of sinuses along the ventral surface of the serous or animal lamina of the embryonic germ disc, which, being suddenly arrested by a large projection of the germ vesicle at the anterior part beyond the vascular and mucous lamina, causes a stagnation in the form of a conical sac, whose apex points forward below the head of the embryo at that time consisting of the mesocrane and procrane, with the visceral segments of the face-kist, and exhibiting three facial clefts.