103 ON THE VISCER4L ANATOMY OF TUE LACERTILIA. [Feb. 7, 



2. Bile-ducts. 



The accompanying drawing (fig. 4, p. 105) illustrates the very 

 remarkable condition of the bile-dncts which characterizes Varanus 

 m/vator ; tbe bile-ducts, both cystic and hepatic, form a highly 

 complicated network, which is found in many serpents, but not, so 

 far as I am aware, in any other Lizard. This fact, however, is not 

 new, but has already been recorded* by Pagenstecher, who, 

 however, has not stated what particular species his observations 

 referred to. I have therefore thought it worth while again to bring 

 tills matter forward, as 1 am able to state the exact species in which 

 this structural pecidiarity occurs. It is important to notice that it 

 is only in Varanus salvator that the cystic and hepatic ducts form a 

 network ; in the other species of Varanus and Monitor which I have 

 liad the opportunity of dissecting the bile-ducts are quite single, as 

 ill other Lacerlilia: I find that Dr. Giinther, who has dissected 

 Regenia ocellata'-, 2i. albigularis, and Monitor niloticus^, makes 

 no mention of any resemblance to Varanus salvator ; I conclude 

 therefore that in the former species also the bile-ducts are single. 



In Alligator lucius (Bronn's ' Thierreichs,' Taf. C. fig. -i) there 

 appears to be just a trace of this network of bile-ducts. 



In the same work Hoffmann refers to the similarity which the teeth 

 of Monitor show to those of the Crocodilia in their development. Mr. 

 Bouhuger has kindly directed my attention to a note iu the ' Zoolo- 

 gischer Anzeiger ' (Bd. x.), by Van Bemmelen, upon the structure of 

 the vessels of the neck in the Sauropsida. From his results it would 

 appear that the Monitors differ greatly from other Lacertilia, and 

 are, in fact, more aberrant than even Hatteria. These facts are all 

 in harmony with my contention that the Monitors should be widely 

 separated from other Lacertilia, and some of them are by no means 

 at variance with my belief that the Monitors show Crocodilian 

 affinities. 



Summary. 



The principal facts recorded in the present paper and the 

 conclusions to which they lead are as follows : — 



(1) The Varanidae differ from other Lacertilia in two important 

 particulars :— in (i.) the occasional complication of the cystic and 

 liepatic ducts, which form a network, (ii.) the presence of a fold of 

 peritoneum, reflected from the lining peritoneum of the abdominal 

 cavity, which surrounds the abdominal viscera. 



(2) This fold of peritoneum has its exact counterpart in Croco- 

 dilia and Aves, where, however, the subdivision of the coelom into a 

 number of separate cavities is carried on still further. 



(3) The Varanidae, therefore, alone (?) of existing Lacertilia show 

 the first beginnings of the subdivision of the coelom, which reaches 

 its extreme in the higher Saur jpsida. 



' Wiirzburg Naturwi.ss. JieitscLir. i. p. 248. 



' r. Z. S. I860, p. CO. " p. Z. S. 1861, p. 109. 



