1906.] VASCULAR SYSTEM OF VARANUS. 611 



other sj)ecies again, I am able to add something to the recorded 

 knowledge of the venous trunks of this — as I consider it — aberrant 

 genus of Lacertilia. 



Hepatic Portal System. — The Lacertilia generally differ from 

 the Chelonia and the Crocodilia in possessing but one anteiior 

 abdominal vein, while the latter, with the exception of Dermo- 

 chelys, possess two*. 



The Ophidia and Hatteria agree with the Lacertilia with some 

 slight exception. 



Thus in certain Boidse f the anterior abdominal divides after 

 the union of the two pelvic roots to reunite again before entering 

 the liver. It is therefore noteworthy that Varanus nilotious (only 

 this species among those which I have examined ad hoc) has, like 

 these Ophidians, an anterior abdominal which is double for a 

 part of its length. In one specimen the arrangement was as 

 follows : — the right root of the anterior abdominal vein before 

 joining the left root gives off two branches ; the first of these is 

 the right anterior abdominal, the second is a vein which brings 

 blood from the ventral surface of the pelvis. The right anterior 

 abdominal is of less calibre than the left or main anterior 

 abdominal trunk ; the two unite not far behind the junction of 

 the portal vein with the conjoined anterior abdominal vessels. 

 In a second specimen of the same species the anterior abdominal 

 was also double ; but I am unable to give exact details. So also 

 with a third individual which was dissected by me a good many 

 years ago, but of whose anatomy I possess notes. 



It will be noted from the above description, that the double 

 character of the anterior abdominal vein in Varanus niloticus 

 may be rather different from that of the Python and nearer to 

 that of the Crocodilia. For in the serpent the double vein occurs 

 after the fusion of the two pelvic roots, while in Varanus the 

 second, smaller, anterior abdominal vein is a direct offshoot of 

 the corresponding pelvic root. It is, that is to say, separate from 

 the very first. Vaixinus does not show, so far as I have observed, 

 any signs of a doubling of the anterior abdominal vein at the 

 liver end. If the comparison between Varanus and the Crocodilia 

 be justified so far as concerns these features, it is clear that the 

 posterior junction between the right and left antei-ior abdominals 

 in Varanus niloticus is to be compaa-ed with the junction in 

 CroGodilus catafkractusX between the two antei'ior abdominals, 

 though the situation of this connecting vessel is not precisely the 

 same in both reptiles. 



Umhilical Vein. — Besides the two epigastric veins already 

 described, there is a median vein which is connected posteriorly 

 with the anterior abdominal and anteiiorlj^ opens into the post- 

 caval vein between the two liver-lobes. Its course was ascertained 



* Bume : " Notes on the Muscular and Visceral Anatomy of the Leathery 

 Turtle," P. Z. S. 1905, vol. i. p. 320. 



f Beddard : " Notes upon the Anatomy of Certain Snakes of the Family Boidse," 

 P. Z. S. 1904, vol. ii. p. 116. % Infra, p. 620. 



