Alimentary Canal.
cl. Cloaca. incl. Cloacal involution. œep. Œsophageal epithelium. pan. Pancreas. th. Thyroid body.
General.
abp. Abdominal pocket (pore). aur. Auricle. cav. Cardinal vein. cauv. Caudal vein. ly. Lymphoid tissue. mm. Muscles. od. Oviduct. pc. Pericardium. pp. body-cavity. sr. Suprarenal body. u. Ureter. vao. Ventral aorta (anterior continuation of bulbus arteriosus). ven. Ventricle. wd. Wolffian duct.
Figs. 1a, 1b, 1c. Three sections through the cloacal region of an embryo belonging to stage O. 1a is the anterior of the three sections. Zeiss A, ocul. 2. Reduced one-third.
1a shews the cloacal involution at its deepest part abutting on the cloacal section of the alimentary tract.
1b is a section through a point somewhat behind this close to the opening of the Wolffian ducts into the cloaca.
1c shews the opening to the exterior in the posterior part of the cloaca, and also the rudiments of the two abdominal pockets (abp).
Fig. 2. Section through the cloacal region of an embryo belonging to stage P. Zeiss A, ocul. 2.
The figure shews the solid anterior extremity of the cloacal involution.