606 MR G. W. BUTLER ON THE [DcC. 3, 



have been demonstrated, by a study of the development, everything 

 points to the conclusion that the circumadiposal cavities are not 

 homologous with any part of the peritoneal cavity proper of other 

 types, hut are altogether extra-peritoneal. 



Again: I do not consider that the membrane "which surrounds 

 the abdominal viscera has its exact counterpart in Crocodilia and 

 Aves" (1, p. 106), except in so far as it is a part of the body-wall. 

 I take it that the " omentum " of Birds is represented in Monitors 

 by the ligament which passes between the stomach and the hinder 

 part of the liver antero-dorsally, and the dorsal face of Beddard's 

 horizontal membrane postero-ventrally. In Monitors, however, as 

 in most other Lizards, it has not acquired that extension in a trans- 

 verse direction which conduces to the formation of a post-hepatic 

 septum in Birds, Crocodiles, and the Teiidse {cf. my paper on the 

 Subdivision of Body-cavity, above, p. 463). 



As to the Crocodiles, Beddard says (1, p. 103) that the horizontal 

 membrane " closely resembles a structure in the Crocodilia which 

 has been described by Prof. Huxley as well as by others." Beddard 

 describes this structure as follows (the italics are mine) : — " This 

 consists of a membrane, partly muscular, which is attached to the 

 pubis and to the abdominal parietes behind, and in the median dorsal 

 line to the backbone ; it entirely envelops the coils of the intestines, 

 so that they are not visible when the body-wall is cut through. 

 Anteriorly this muscular expansion is attached to the fibrous com- 

 partments in which are lodged the two lobes of the liver ; the lungs 

 are thus shut off from the abdominal cavity; this membrane bears 

 on the ventral surface the anterior abdominal veins : there is evidefitlij 

 a close similarity, so far, between the Crocodile and the Lizard ; 

 furthermore, in both animals the lateral regions of the membrane 

 are connected with the lateral parietes by fibrous bands, and in both 

 the fat-body lies outside of the membrane and outside of the 

 abdominal cavity ; the reproductive glands and the kidneys have a 

 similar relation to the membrane in both types : in the Crocodile, as 

 in the Lizard, the reiwoductive glands and the kidneys are separated 

 by the membrane ; the former lies within, the latter without, the 

 abdominal cavity. Th.e only diiferences are that in tlie Crocodile 

 the membrane is largely covered by muscular tissue, and that instead 

 of simply passing over the liver and stomach, it becomes connected 

 with special sheaths enveloping these organs. In these points the 

 Crocodile, as Prof. Huxley has pointed out, resembles birds. The 

 above considerations point, in my opinion, to an unmistakable 

 resemblance between the Monitor Liaards and the higher Saui-o- 

 psida." 



I have not at present observed a well-marked circumadiposal space 

 round the subperitoneal fat-bodies of Crocodiles. But if, as I 

 take it, the membranes above referred to in Monitors and Crocodiles 

 are but the inner layers of the body-wall, they are doubtless homolo- 

 gous to a certain extent. I would add, however, with reference to the 

 statement that the membrane in Crocodiles is " largely covered with 

 muscular tissue," that (in my opinion) the ventral fat-masses that 



