1906.] ANATOMY OF THE OPHIDIA. 31 



Snakes. I have already dealt with Eryx * and Eunectes t. I do 

 not find that Jacquart's illustrations conform absolutely to my own 

 observations ; but it may be, of course, that this system shows 

 some variations. I find that, as in other Boidse, the system of 

 longitudinal parietal vessels is chiefly developed upon the left side 

 of the body, but not so exclusively so in Python as in Eunectes. 

 The left parietal vessel commences posterioi-ly at about the end of 

 the lung, that is to say very considerably behind the liver. 

 Anteriorly it ends at about the level of the bifurcation of the 

 aorta into its right and left moieties. 



Between these two points the vessel is almost, if not absolutely, 

 continuous. It receives the intercostals as they emerge froxn the 

 parietes, and sends off branches to the liver and to the alimentary 

 canal in this region. These branches are at least partly in- 

 dependent of each other ; that is, separate branches pass to each 

 viscus or perhaps rather from one to the other. The veins which 

 pass to the liver enter the anterior extension of the portal vein 

 lying upon the liver, and there are at any rate nine of them. 

 Anteriorly the longitudinal parietal ends in a bifurcation, and 

 behind this there is another branch, which, like one half of the 

 anterior bifurcation, lies upon the right side of the body, distri- 

 buting its branches to the intercostal spaces of that side of the 

 body. In Eunectes, although the left longitudinal parietal vessel 

 is the only one developed, it i-eceives twigs from both sides of the 

 body, but there is no development of a longitudinal trunk or 

 trunks upon the right side. As in other Snakes, a particularly 

 strong branch from the longitudinal parietal passes up to the 

 portal trunk just before the latter reaches the liver. 



The main points in the foregoing notes upon the veins of Python 

 sehce to which I desu-e to call attention are the following : — 



(1) The double origin of the anterior abdominal vein, one root 



from each renal afierent vein, as in Eryx jacidus and in 

 the Lacertilia without exception. 



(2) The pi'olongation of the renal afi"erent vein beyond the 



kidney along the sperm- duct, this region being, like the 

 renal afferent, a persistent posterior cardinal. 



(3) The existence of a trace of the umbilical vein, which persists 



in its entirety in Eunectes. 



(4) The paired main trunks of the neck distinguish Eunectes 



from Python, where, as has been also shown by others, 

 there are only three trunks and the paired jugulars are 

 not symmetx'ical in size. 



(3) Some Notes upon Ilysia scytale. 



The following notes are the result of the examination of a 

 single specimen of Ilysia scytale which has been in my possession 

 for some time. 



* P. Z. S. 1904, vol. ii. p. 118. f Above, p. 24. 



