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



reproductive glands and their ducts. From this it is not surprising 

 to find that it terminates anteriorly in front of the reproductive 

 organs, the body-cavity of either side being obliterated over a longer 

 or shorter area. 



§ IV. (ii.). The Unpaired " Gastric" Peritoneal 

 Space of the Left Side. 



Between the hinder end of the right liver-lobe and the anterior 

 end of the right reproductive gland the main^ right half of the 

 peritoneal cavity is unrepreseuted in the male ; and in the female it is 

 only represented (as described above) by a narrow peritoneal funnel 

 or tube which sometimes extends but little in advance of the ovary. 



On the other hand, on the left side there is, with few exceptions, a 

 distinct peritoneal space to be made out in the pyloric region. 

 Retzius [(1) p. 89, and (2) p. 515], describing Python bivittatus, 

 notices both this and the space which will be later referred to 

 [§ IV. (iv.)] as the omental one. 



To find this gastric space in any Snake, we, after the preliminary 

 easing away of the body-wall described above (§ IV. (0)), mark the 

 point at the end of the stomach where, about opposite the hind end 

 of the gall-bladder, it is often slightly bent (just where its thick- 

 walled part ends). Then, carefully lifting up and cutting through 

 the membranous tissue that wraps round the left and ventral sides 

 of the posterior end of the stomach, we shall in nearly all cases 

 {see § III. and § V,) find a distinct serous space, which, in the region 

 described, wraps round the stomach on its ventral and left sides 

 (the " blind sac " of Retzius) ; when, as sometimes happens, this 

 is continued forwards by a narrow canal (" left serous canal " of 

 Retzius), this latter, as a rule, lies more ventrally than laterally 

 to the stomach itself. 



This gastric sac was, among the forms I examined, best developed 

 in a specimen of Coelopeltis lacertina, where it extended from a 

 point 1 1 inches behind the gall-bladder forwards, so as to slightly 

 overlap the left liver-lobe. It is, however, here, as apparently in all 

 Snakes, divided off from the peritoneal sac that surrounds that liver- 

 lobe. It is also well developed in some specimens of Zamenis 

 gemonensis (a common Italian Snake) and in the various types of 

 Pythonidse examined (viz. Eryx, Enygrus, Python). It was also 

 distinct in Compsosoma and Lamprophis; and in fact I ascertained its 

 presence in all the species examined, with the exception of a few 

 marked (e) on the list in § III., and it not improbably occurs in some 

 of these also. 



However, it is developed to a very different degree in different 

 species and in different individuals of the same species. Thus it 

 vjill very likely not be found in many specimens of Tropidonotus 

 natrix, while it would appear (Elaphis, Zamenis) that it may be larger 

 in the male than in the female. 



^ There is, however, in many cases, a more or less marked " omental " space 

 traceable {cf. § IV.). 



