co) 
ca) 
Or 
Frederic T. Lewis 
of which is the ventral anlarge. P, ¢. Peri-cardial cavity, P. V, Pulmonary 
vein. Sp. ¢, Spinal cord. St, Stomach. ¢t, Posterior portion of the tongue. 
T. i, Tubereulum impar. Tra, Trachea. Um. d, Right umbilical vein. Ven, 
Left ventricle. V. mes, Superior mesenteric vein. V. port, Portal vein. V. 
vi, Vitelline vein (Omphalo-mesenteric. W. D, Wolffian duct. «, Anasto- 
mosis between the right and left cardinal systems. Yk, Yolk sac. Yk. s, 
Yolk stalk. x 13.5 diams. 
PLATE IV.—Pig Embryo of 12.0 mm. Reconstruction from transverse sec- 
tions, Series 5. 
The section is on the right of the median plane, and shows chiefly the 
heart and venous system. A, Umbilical artery. a, Aortic septum. All, 
Allantois. Ao, Aorta. Au, Right auricle. 6, Bundle of trabeculae. c¢, wall 
between bulbs arteriosus and auricle. card’, card”, Superior and inferior 
sections of the posterior cardinal vein. cl. 1, cl. 2, cl. 3, el. 4, Entodermal 
pouches and their pharyngeal openings of the corresponding gill clefts. c¢. 
om, Dotted outline of the omental or lesser peritoneal cavity. d, Left duct of 
Cuvier. D. C, Right duct of Cuvier. D. V, Ductus venosus Arantii. F. W, 
Foramen of Winslow. F. pp, Pleuro-peritoneal foramen. gen, Genital tu- 
berecle. G. R, Genital Ridge. Jug’, Jug”, Jugular or anterior cardinal vein. 
Li, Liver. l. s, anlage of the lateral sinus. ma, Transverse vein. P. Pul- 
monary artery. p. ¢, Pericardial cavity. Pl, Dotted outline of pleural cay- 
ity. tec, Rectum. Sc, Subeardinal vein. Sel, Subclavian vein. sls, Anlage 
of the superior longitudinal sinus. Ur, Ureter. Um. d, Right umbilical vein. 
v, Valves of the sinus venosus. Ven, Right ventricle. V. H. OC, Vena hepatica 
communis. v. op, Ophthalmic vein. V. P, Portal vein. W. b, Wolffian body. 
W. D, Wolffian duct. «, Anastomosis between the right and left cardinal 
systems. x 13.5 diams. 
