312 MR. F. E. BEDDARD ON THE VASCULAR AND [May 1, 



slightly better developed on the right side than on the left in 

 P. molurus. This vein ran nearly to the cloaca. It is connected 

 by numerous branches with the renal afferent up to the point 

 where the latter reaches the kidney ; but after that point there 

 are no more branches to the renal afferent until the latter 

 leaves the kidney antei-iorly. Here the vessel is connected with 

 he anterenal prolongation of the renal afferent by one branch, or 

 rather ends in it, for the lateral dorsal is not itself prolonged 

 beyond the kidney, although numerous intercostal veins arise 

 separately in front of the kidney and join the post-cardinal, as 

 I regard this forward prolongation of the afferent renal. The 

 absence of any intercostals running from the parietes in the region 

 of the kidney across that gland to the renal afferent vein, such as 

 are met with in Erythrolamprus and Coluber'^', may prove to be a 

 distinguishing feature of the Boine Snakes. 



Python regius may be an exception. In an injected example 

 of that snake, the renal afferent vein was seen to receive from the 

 parietes a branch just behind the kidney and one a little way in 

 front. Just behind the latter, and therefore arising from the 

 parietes just in the kidney- region, was a vessel of which I could 

 not detect the ending. It may, however, very well have reached 

 the post-cardinal in front of the kidney. In this species there is 

 no continuous lateral vein in the kidney-region. And as the 

 specimen was well injected in this region, I am confident of this 

 difference from P. molurus. 



Azygos Vein. — The azygos vein in Boa diviniloqua is in many 

 respects much like that of other Snakes — that is to say, it is not 

 very extensive, extending down the body not much beyond the 

 beginning of the liver. It gives off branches of two kinds, both 

 of which are not always developed in Snakes, or are, at least, not 

 always visible in examples which I have dissected. These branches 

 are firstly those which flow from the body close to the median 

 ventral line, on the right side of the vertebral column of course, 

 i. e. on that side which the azygos lies upon. Besides these there 

 is a series of veins which run so superficially to the lateral 

 parietes as to lie actually above the surface of the body-wall. 

 They are supported by membranes, and are not in close con- 

 nection with the parietes. Two of these veins arise from the 

 main azygos trunk before the latter reaches the level of the 

 parietes. The main trunk of the azygos divides into two branches 

 soon after the region of the heart. An outer branch runs back 

 for some distance before again approaching the median line and 

 giving branches to the intervertebral spaces. These branches 

 generally are fewer than the intercostal spaces, and they must 

 therefoi'e divide within the parietes. 



The azygos, then, of this species supplies two regions of the 

 body. It draws blood from the parietes in the immediate neigh- 

 bourhood of the dorsal median line, and also from the body-wall 



* See p. 502 (text-fig, 87) and p. 503 (text-fig. 



