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Show 612 MR. F. E. BEDDARD ON THE [May 29, accurately. It does not form part of the liver circulation, but is definitely connected with the general circulation by means of the postcaval. It seems to me to be possible, although I am unable to offer any embryological evidence, that this vein is a persistent umbilical. It has very much the same relations as has the vein in Heloderma *, which is, as I think, to be referred to a persistent umbilical, except for the fact that it communicates in Varanus with other veins ; this is not the case with the umbilical of Heloderma, or of snakes, in which it occurs with one exception. That exception is Bitis nasicornis f , where I found that the undoubted umbilical vein was connected with the epigastric system. There is thus a precedent for a persistent umbilical connected in the adult with other veins among the Squamata. The same is the case with the persistent umbilical of Birds and of Echidna %. Thus the connection with the parietal and other veins is not at the least evidence against regarding this vein in Varanus as the persistent umbilical. Moreover, the connection does not occur in both of the species, in which I have detected what I believe to be a persistent umbilical. In Varanus niloticus the umbilical is connected just at its entrance into the postcaval with a forwardly running branch. On the other hand, in Varanus exanthematicus the vein had no such branch and appeared to end posteriorly without making any connection with the epigastric system or being elsewhere connected with the parietes. I have not any notes or sketches showing this vein in Varanus griseus, and its occurrence is not mentioned by either Corti § or Hoch-stetter jj. It is particularly difficult to prove a negative in the case of veins ; and accordingly I prefer rather to dwell upon the jyresence of the vein that has just been described in two species of Varanus. Azygos and Lateral Parietal Veins.-On the right side of the body is a vein which seems to correspond to the azygos of other reptiles, but to be of more limited extent than is often the case. The vein, in fact, plunges into the thickness of the parietes directly it reaches the side of the vertebral column. In another specimen the azygos consisted of two branches, which also disappear into the parietes at once. The vein of course arises from the l ight vena cava superior. I am inclined to think that Hochstetter is in error when he speaks of a vessel obviously corresponding in the following words :-" Eine dritte sehr maclitige [Intervertebralvene] findet sich reclits als die vorderste im Brustraum und gelit in weitem Bogen in die Y. cava superior sinistra ein." From this azygos, before it reaches the side of the vertebral column, arises the posteriorly running lateral abdominal or, better, lateral parietal vein, as I propose to call it. The vessels have already been to some * Supra, p. 602. f " Contributions to the Anatomy of the Ophidia," P. Z. S. 1906, vol. i. p. 41. J Cf. Beddard : " Anterior Abdominal Vein in Echidna," P. Z. S. 1884, p. 5 5 3 ; and Hochstetter in Semon, " Zoologische Forschungen," &c., Jen. Denkschr. 1895. § Loc. cit. (on p. 610). || Loc. cit. (on p. 610). ■J Italics mine. |
