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Show 1906.] VASCULAR SYSTEM OF VARANUS. 617 supported by a fold of membrane wliich attaches the " Hohlvenen-fortsatz " of the liver to the parietes and forms a pocket as in Iguana and some other Lizards, including Heloderma. The single vein is not, however, a generic character of Varanus. It is single in V. exanthematicus and in V. ocellatus; but in two out of four examples of Varanus niloticus which I have dissected the conditions were different. In two small specimens there was only a single vein as in other species ; in one large individual there were distinctly twTo veins, which reached and penetrated the liver separately ; in the fourth specimen, also large, and a female like the last, there were also two veins, which, however, joined soon after their emergence from the parietes to form a single trunk entering the liver as such. In the two small individuals which were males (and not very well preserved in spirit) it seemed to me that there was a junction between two veins quite close to the body-wall. The more prevalent arrangement among the Lacertilia is that there are several of these veins * running a parallel course to the liver. In addition to this vein (or, rarely, veins) the liver also receives blood from the dorsal or dorso-lateral parietes in its anterior region. In Varanus griseus Hochstetter has mentioned a vein- 11 eine Zw^eite Leibeswandvene dringt direkt in die kopfwarts gerichtete Spitze des rechten Leberlappens, diese wurzelt in der entsprechenden Partie der dorsalen Leibeswand " t. There is no further description of the vein. The vein in question is accurately described by Hochstetter as entering the very tip of the right lobe of the liver. It corresponds exactly in position to a vein from the stomach which enters the tip of the left lobe +. The origin of the vein from the parietes is of some interest. It originates in fact from a longitudinal vein, the lateral abdominal, whose relations to other veins has been already described. The same vein occurs in Varanus niloticus, where I found it fuller than in the example of V. griseus. The same vein plainly exists in V. exanthematicus, with the same connections with the vein of the dorso-lateral parietes. The existence of these venous affluents of the portal system is of interest in comparing Varanus with other Reptiles. In the presence of vessels from the dorsal parietes joining the liver - circulation anteriorly as well as posteriorly, Varanus differs from Lacerta, Iguana, and some other Lacertilia. It agrees, however, in this with Heloderma, as has been already set forth in the present communication^ The connection, however, in this latter instance is with the vertebral vein, while in Varanus the hepatic affluent in question is only indirectly connected with the vertebral vein system, and arises directly from the lateral abdominal vein, which * I may take this opportunity of referring to another character which I have found onlv in one species, and not in a considerable number of others In V.gouldi the apex of the heart has a gubernaculum tying it to the pericardium. I his is generally stated to be absent, and I have not found it in V. bengalensis, V. griseus, V. niloticus, and V. exanthematicus. % f Loc. cit. p. 466. S V. infra, p. 618. § T . supra, p. 606. |
