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Show ANATOMY OP CERTAIN SNAKES. 1 1 3 murinus, Eryx johni, and Eryx conicus each kidney had only one renal artery. In Eryx jaculus there was some variation in the two examples studied. In one there were two renal arteries for each kidney; in the other the left kidney had two arteries, the right only one. Here, it may be remarked in passing, is an apparent difference between the two species of Eryx investigated by me, which I shall refer to again later. Now, as the kidneys of Eryx are very short * and those of Coluber catenifer long, as they are in the majority of snakes, it might be held that the arterial blood-supply had merely a relation to length. That the character is one peculiar to the Boidie seems to be shown by the case of Eunectes murinus, for in this serpent there is only one renal artery to each kidney; and yet those organs, in the individual which I dissected, measured respectively 15| and 12^ inches in length. § Veins of the Posterior Abdominal Region in Eunectes. The caudal vein emerges from the thickness of the parietes some way behind the cloaca. When it reaches the level of the cloaca, two veins, asymmetrically placed with regard to one another, join it. I suppose that these are the equivalents of the ischiadic veins of Lizards. Further forward, between the cloaca and the very anteriorly situated kidneys f , the caudal vein divides at once into three branches. The middle one of these is the right and larger anterior abdominal vein. To the left of this arises the afferent renal vein of the left kidney, and to the right of the anterior abdominal a vein which runs over the viscera to the dorsal surface of the body, where it enters the parietes to the left of the middle line, after running both forwards and backwards for a short distance. I am inclined to regard this vein as the equivalent of the lateral abdominal vein of its side in the Lacertilia. Its place of origin agrees with such an homology, and the shortness of its course within the body-wall is no reason against the comparison, since it is of varying length among the Lacertilia. It might be held that this vein is in reality only the proximal end of the left afferent renal which has lost its connection with the remainder of that vein, were it not for the conditions observable in Eryx to which I recur later (see p. 114). There is, in fact, no afferent renal on this side of the body springing from the caudal vein and corresponding in origin to the fully developed afferent renal, whose origin on the other side of the anterior abdominal has been already referred to. It rises, I presume, from the caudal vein further back. * In Eryx johni, which measured 26 inches from snout to vent, the kidneys were respectively f inch (right kidney) and 1 inch (left kidney) in length. In E. jaculus of 15f inch length to vent, the kidneys were proportionately larger, i. e. f inch and 1 inch, and in E. conicus of 27 inches this was also the case : they measured 1L and l i inch. f The kidneys are well known to occupy a very anterior position in the Hoidie. It has not, I think, been noted that Eryx as well as Eunectes agrees in this with Python and Boa. P r o c . Z o o l , S o c .-1904, V o l . II. N o . YIII. 8 |