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Show 1904.] ANATOMY OF CERTAIN SNAKES. 1J 7 gemonensis. I take it that the posterior1 bifurcation of the anterior abdominal vein in the last-mentioned Colubrine snake (and possibly in Cciusus and other forms) is a reminiscence of its former origin by two roots from the renal afferent veins as in the less modified Lacertilia, and, as I have already shown, in the especially " Saurian " Eryx jaculus and Eryx johni. It is clear from the foregoing, that the somewhat divergent opinions of previous authors are partly due to actual differences in the abdominal and afferent renal veins of different Ophidia, to our knowledge of which I have been able to add something. It is furthermore clear that the Boidfe contrast with other Ophidia, so far as observation has gone, in their greater approximation to the Saurian type of organisation ; they are, in fact, more primitive than other Ophidia. In these Ophidia alone is the anterior abdominal vein connected with one or both of the afferent renals, and in them there is generally doubling of the anterior abdominal vein in front of the junction of its constituent veins. Of all the Boidse whose anatomy is known, Eryx jaculus (not E. conicus) comes nearest to the Saurian type in that its anterior abdominal vein arises from two distinct roots, one from each of the renal afferent veins. § Remains of Cardinal Veins. In comparing the venous system of the adult Tropidonotus with that of the adult Lacerta, Dr. Hochstetter * arrived at the conclusion " dass das Venensystem der Lacerta auf einer etwas niedereren Entwicklungsstufe strehen geblieben ist als das von Tropidonotus. Bei Lacerta ist das System der Vertebralvenen noch erhalten, wahrend es bei Tropidonotus nahezu vollig gesch-wunden ist." Hochstetter's statements are also accurate when applied to other Colubrine snakes. I have examined Lioheterodon madagascariensis with some care from this point of view. In that snake there is hardly any development of vertebral veins, such as I shall describe immediately in the Boidse. About halfway down the liver, however, is a longitudinal vessel running for a short distance, from which arises a tributary to the hepatic portal system. Another Colubrine snake, viz. Zamenis gemonensis, showed an interesting persistence of a portion of the posterior-cardinal vein precisely comparable to what is to be found in the Chamseleon f and in Pygopus £. The afferent renal artery in front of the left kidney, instead of ending, as is usual, towards the anterior end of that gland, passes beyond it and imbeds itself in the body-wall to the left of the median dorsal line. I could find nothing to correspond on the right side. If really absent-- and I am convinced that there is at least nothing really conspicuous- this is another example of the asymmetry of Ophidian * Morph. Jahrb. xix. p. 493. f Hochstetter. loc. cit. p. 462, and Beddard, Joe. cit. infra. J Beddard, " Contributions to the Anatomy of the Lacertilia, No. 3," P. Z. S. 1904, vol. ii. p. 12. |