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Show 494 MR. G. w. B U T L E R O N THE [June 14, posthepatic septum, which was also seen forming out of the ligament of the stomach. The liver-sac of the right side (fig. 2B, Pl) is still continuous, by a long and very narrow peritoneal tubule (fig. 3B, P"), with the main posterior peritoneal space. Following this narrow tube backwards from the liver-sac, we find that it runs externally to (on the right side of) the postcaval and vitelline (or portal) veins, and that it contains a minute forward continuation of the funnel of the oviduct, represented by a raised groove on the wall of this small space. As this tube of communication is now so small, and has no apparent use, it is not surprising that it should be obliterated in the adult. In the figure (3B) we see, cut through, a very small cavity, on the right side of the stomach, in the corner between it and the lung. This must be the remains of the " omental space" as to the persistence of which in the adult of this species I am not certain (see list). Lastly, as to the gastric space. This is also seen in section in fig. 3B (Ps). Following the sections backwards, we find that it is still freely continuous with the posterior portion of the peritoneal cavity. Finally, at this stage, sections through the region of the pancreas show that the ventral ligamentous attachment of the alimentary canal to the adjacent body-wall becomes here very broad; so that we can easily understand how, when the alimentary canal comes to be bent and' folded on itself, as it here does later on, the gastric sac might become closed posteriorly, in somewhat the same way as did the left liver-sac. The permanent kidneys (which in the preceding stage were only just making their appearance, and then had the peritoneum extending as a backwardly directed pocket external to each and covering their mesial surface) are now fairly developed, and it is found that the posterior part of each lies completely outside the body-cavity. In the adult they come to lie entirely outside it. § VII. The Subdivisions of the Body-cavity in Snakes compared with those in other Sauropsida. [I here refer to the figures illustrating my previous paper (5).] (i.) The posterior peritoneal space seems to have its exact homologue in Crocodiles [(5) figs. 42, and 43, 3], and it is very similar to the posthepatic cavity in the Lizard Tupinambis [(5) fig. 31, 3] or a Bird [(5) figs. 14-18, 3); but in the Bird there is on the left side and in Tupinambis on both sides [(5) fig. 32, o, o'] a connection with the anterior part of the body-cavity. In fact:- (ii.) Snakes agree with Birds (e. g. Gallus, Anas), Crocodiles, and the Lizard Tupinambis in having a septum across the body-cavity behind the liver (posthepatic septum). In Birds and Tupinambis this septum is incomplete. (iii.) The gastric space seems to have an almost exact homologue |
