606 MR. G. W. BUTLER ON THE [Dec. 3, 
have been demonstrated, by a study of the development, everything 
points to the conclusion that the cireumadiposal cavities are not 
homologous with any part of the peritoneal cavity proper of other 
types, but 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-hepatie 
septum in Birds, Crocodiles, and the Teiidee (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 evidently 
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 reproductive glands and the kidneys are separated 
by the membrane; the former lies within, the latter without, the 
abdominal cavity. The only differences are that in the 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 Lizards and the higher Sauro- 
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 acertain 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 
