494 MR. G. w. BUTLER ON THE [June 14, 



posthepatic septum, which was also seen forming out of the ventral 

 ligament of the stomach. 



Tlie liver-sac of the right side (fig. 2^, P') is still continuous, by a 

 long and very narrow peritoneal tubule (fig. 3^, 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 communi- 

 cation is now so small, and has no apparent use, it is not surprising 

 that it should be obliterated in the adult. 



In the figure (3^) 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. 3^ (P")' 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 pan- 

 creas show that the ventral ligamentous attachment of the alimen- 

 tary 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 

 gast7'ic 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. 3 1, 

 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 se|)tum is incomplete. 



(iii.) The gastric space seems to have an almost exact homologue 



