The communication existing by means of the cardiac vein between the heart and the hepatic afferent system may suggest, but _purely for illustrative purposes_, the direct connection of the umbilical vein with the heart by the ductus venosus in the mammalian embryo (cf. schema Figs. 250-256). =3. Reptile.=--In _Iguana_ the renal portal system is well developed. The caudal vein, returning the blood from the tail and the cavernous tissue of the genital organs, continues for a short distance upon the fused caudal end of the two kidneys (Fig. 269) and then divides into two afferent renal veins which ascend on the ventral surface of the glands, giving branches to the renal capillary system. About the middle of the kidney each afferent vein is joined by a large transverse branch from the abdominal vein (Fig. 266). [Illustration: FIG. 266.--Systemic veins of _Iguana tuberculata_. The alimentary canal and appendages, together with the hepatic portal vein and the intrahepatic segment of the postcava, have been removed. The liver occupies the space between the divided ends of the postcava. The vertebral vein represents the rudimentary proximal segment of the postcardinal vein corresponding to the mammalian azygos vein. (Columbia University Museum, No. 1320.)] [Illustration: FIG. 267.--Veins of _Iguana tuberculata_. Connection of systemic veins with sinus venosus of heart. The rudimentary system of the vertebral (azygos) veins and their proximal connection with the subclavian vein are shown. (Columbia University Museum, No. 1859.)] [Illustration: FIG. 268.--Corrosion preparation of venous system of liver in _Iguana tuberculata_. The hepatic portal system and its connection with the abdominal vein, as well as the relation to the postcava, are shown. The preparation supplements Fig. 266, showing the parts which have been removed in the latter. (Columbia University Museum, No. 1860.)] [Illustration: FIG. 269.--_Iguana tuberculata_, male. Genito-urinary tract, dorsal view, with renal-portal, postcardinal, and postcaval veins. (Columbia University Museum, No. 1862.)]