1892.] BODY-CAVITY IN SNAKES. 485 



' Forms of Animal Life,' 2nd ed. p. 69). From my tabulated 

 notes I find that the straight terminal portion of the intestine seldom 

 projects at all into the body-cavity, and that the less folded portion, 

 immediately preceding this, seldom (as in Ccelopeltis lacertina, 

 Crotalus durissus, Compsosoma melanurum, and Python) has any- 

 thing that can be called a mesentery. As to the zigzag part of the 

 intestine that follows the stomach, the peritonenm (as so often 

 noticed) does not follow the individual bends, but merely covers the 

 zigzag as a whole. In fact the intestine of Snakes, as a rule, 

 intrudes upon the peritoneal cavity less than in any other Vertebrates. 



Secondly, as to the kidneys '. With rare exceptions, the permanent 

 kidneys in Sauropsida (unlike the Wolffian bodies of the embryo, 

 and the kidneys of certain Mammalia) do not project freely into the 

 body-cavity, but are in great part, if not entirely, situated out- 

 side it ^. Snakes are no exception to this rule. In Boa constrictor, 

 it is true, I have found the kidneys hanging freely in the body- cavity, 

 as in certain Amphisbaenidae, but this is the only case I have 

 found among Snakes. The only other Snakes in which I have found 

 any part of the kidneys projecting into the body-cavity are Typhlops, 

 Ccelopeltis, and the Pythonidce, and in these cases the intrusion is 

 but shght. In all tiie other forms examined (see list §111.)^ the 

 kidneys lie entirely outside the peritoneal cavity, and do not project 

 at all into it. It is interesting to note that this exclusion of the 

 kidneys from the body-cavity in Snakes is, like the absence of this 

 cavity round parts of the alimentary canal, not primary. That is to 

 say, when, at a comparatively late embryonic stage, the permanent 

 kidneys first begin to develop, they in part project into the 

 peritoneal cavity, as is the case in the adults of some (and perhaps 

 most) Lizards. 



Thirdly, the only other organs whose relations to this hinder 

 peritoneal space we have to consider are the reproductive ones : 

 and these in both sexes (and as I believe to be the case in all Verte- 

 brates) project freely into the body-cavity. 



Bearing, then, in mind that the kidneys of Snakes are with rare 

 exceptions wholly outside the [leritoneal cavity ^ and that the 

 intestine commonly has no mesentery and bulges but little into the 

 body-cavity, so as in individuals of some species {Liophis meremii) 

 to appear to have almost entirely receded from it, it will be readily 

 understood that this hinder jjeritoneal space may occasionally 

 be reduced in Snakes to little mure than a tube containing the 



^ I add these remarks as to the kidneys because those organs are usually 

 referred to in discussing the relations of the peritoneum, and the impression is 

 sometimes conveyed that there is something unusual in the exclusion of the 

 kidneys from the body-cavity. 



^ The AmphisbKuidge [e. g. A. darwinii, Lepidosternon scutigermn, and to a 

 rather less extent A. alba and F achy calamus hrevii\ are the only marked 

 exceptions I know of besides the Boa constrictor. 



^ I could not ascertain the relations in Lamprophys, Hydrophis, and Crotalus, 

 but have no reason to suspect them to be exceptional. 



■* The lymph-space mentioned above which may occur round them must not 

 be mistaken for part of the peritoneal cavity. 



