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Show 484 MR. G. W. BUTLER ON THE [June 14, and Blanchard (3). If we carefully, with the aid of a seeker and pair of scissors, open up the ventral wall of this space, we shall find that it tapers off posteriorly on the ventral side of the rectum and appears to end at a small distance in front of the cloaca (varying in different species). On the other hand, we find that it ends anteriorly in front of the reproductive glands. It is in fact, like the corresponding space in Birds, Crocodiles, and Tupinambis, an intestino-genital cavity. As the right reproductive gland lies, in Snakes, in advance of the left, this posterior peritoneal space extends forwards farther on the right side than on the other. In the male we shall probably have no difficulty in making out the anterior limits of this space, just in front of the anteriorly rounded testes. But in the female it may not be always easy to say exactly where this space does end anteriorly. If we follow the oviduct of either side forwards, we find the anterior end of its funnel continued as a thread into a narrow, forwardly directed, funnel of peritoneum. On the right side [cf. (3) pp. 100, 101] this narrow peritoneal funnel or tube runs forwards just externally to the portal and postcaval veins, and is the remnant, as will be explained later, of the right half of the peritoneal cavity in this region, which, down to a comparatively late embryonic stage, persists as a narrow tube (fig. 3B, P°) placing the posterior peritoneal space now described in communication with that in which the right lobe of the liver lies. Similarly with the small funnel on the left side. W e can frequently tell approximately where these peritoneal tubes or funnels end, and this was especially clear in a specimen of Heterodon d'orbignii. While sometimes it is hard to say this, it is not very important to know the exact point at which such tapering tubes end, especially as it is, in nearly all cases, perfectly clear that the anterior peritoneal spaces into which they might be expected to lead are closed behind\ The wonder is not that where, as in the females, these forwardly directed peritoneal funnels occur they should vary as to their extension forwards, but that the original embryonic continuity of the peritoneal cavity on either side is, so far as I can ascertain, never maintained in the adult. Before leaving this hindmost division of the peritoneal cavity, which, as stated, extends in the male (and except for insignificant tubular processes in the female also) from the anterior border of the reproductive organs to a point on the rectum usually not far from the cloaca, it may be well to say a few words as to the viscera which project into it. As stated in § II., the relations of the peritoneum to the alimentary canal have been repeatedly noticed by writers on Snakes, from Meckel (loc. cit.) to the present day (cf for instance Rolleston, 1 It is only rarely that the right half of the liver tapers off backwards along the course of the posterior vena cava. W h e n this is so, it m a y be sometimes difficult to say exactly where the tapering liver-sac ends. [Liophis meremii, Vipera arietans, V. nasicornis, Crotalus durissus,] |