1904,] ANATOMY OF CERTAIN SNAKES. 117 



gemonensis. I take it that the posterior bifiu'cation of the 

 anterior abdominal vein in the last-mentioned Colubrine snake 

 (and possibly in Causus 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 Boidae 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 

 Boida3 whose anatomy is known, Eryx jacuhis (not E. conicios) 

 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 Troindonoiiis 

 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 accui-ate 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 half- 

 way 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 gemov en sis, 

 showed an interesting persistence of a portion of the posterior 

 cardinal vein precisely comparable to what is to be found in the 

 Chamaeleon t and in Pygopus %. The afferent renal artery in 

 fi-ont 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 con- 

 spicuous — this is another example of the asymmetry of Ophidian 



* Moi-ph. Jahrb. xix. p. 493. 



t Hochstetter, loc. cit. p. 462, and Beddard, loc. cit. infra. 



t Beddard, " Contributions to the Anatomy of the Lacertilia, No, 3," P. Z. S. 

 1904, Tol. ii. p. 12. 



