612 MR. F. B. EEDDAED ON THE [May 29, 



accurately. It does not foriXL 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 nasicoriiis f, where I found that the un- 

 doubted 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 

 oi 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 Varamos 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 Vai-anus griseus, 

 and its occurrence is not mentioned by either Corti § or Hoch- 

 stetter ji. It is particularly difficult to prove a negative in the 

 case of veins ; and accordingly I prefer rather to dwell upon the 

 presence of the vein that has just been described in two species of 

 Vai'anus. 



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 right 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 machtige [Intervertebralvene] 

 findet sich rechts als die vorderste im Brustraum und geht in 

 weitem Bogen in die V. cava superior sinistra^ ein." From this 

 azygos, before it reaches the side of the vertebral column, arises 

 the posterioi"ly running lateral abdominal or, better, lateral parietal 

 vein, as I pi'opose to call it. The vessels have already been to some 



* Supra, p. 602. 



t " Contributions to the Anatomj^ of the Ophidia," P. Z. S. 1906, vol. i. p. 41. 

 j Cf. Beddard : "Anterior Abdominal Vein in Echidna," V. Z. S. 1884, p. 553; 

 and Hochstetter in Semou, " Zoologische Fovschungen," &c., Jen. Uenkschr. 1895. 

 § Loc. cit. (on p. 610). || Loc. cit. (on p. 610). 



^ Italics mine. 



