228 MISS M, POOLE ON THE DEVELOPMENT OF THE __[ Mar. 2, 
consequence of the absence of ‘air-sacs being indicated by the 
apertures in thisregion. That part of the septum which is present 
dorsally, he accounts for by the need of some such transverse 
membrane to carry the inferior vena cava to the liver, in the absence 
of the pulmo-hepatic ligament present in most other Lizards; and 
suggests that it may have been produced by the vena cava, 
instead of developing as in other Lacertilia and Birds in tissue 
continuous with the right pulmo-hepatic ligament, arising in a 
lateral expansion of the median dorsal mesentery. 
In many species of Monitor and Varanus, Beddard [3] describes 
a horizontal (post-hepatic) membrane which covers the intestines 
when the body-wall is opened ventrally. He says it is attached 
anteriorly to the ventral body-wallin the middle line, and dorsally 
to the spinal column, while to the lateral parietes it is attached 
here and there by membranous bands. ‘It passes over the lobes 
of the liver and the stomach and shuts off the lungs from the 
abdominal cavity. The umbilical ligament dividing the two liver- 
lobes is present, and is attached to the dorsal side of the hori- 
zontal membrane. This horizontal membrane also separates the 
kidneys from the reproductive glands; the latter lie internally to 
it; the kidneys are placed outside it....The fat-body when 
present lies below the membrane, and is therefore shut off from 
the abdominal cavity.” Butler [11], however, describes how the 
fat-bodies in reptiles are typically placed outside the ccelom and 
surrounded by distinct extra-peritoneal cavities-—the circum- 
adiposal spaces. He therefore considers it probable that the 
greater part of this horizontal membrane described by Beddard 
is the lining peritoneum which has become almost completely 
separated from the abdominal walls by the great extension of the 
circumadiposal cavities outside it. This view as to the nature of 
Beddard’s horizontal septum seems to be further borne out by the 
position of the umbilical ligament, which he describes truly as 
being attached to the dorsal surface of the membrane; for in 
birds and crocodiles, where I believe a real post-hepatic septum 
exists, the ligament is attached to the ventral surface, and thence 
passes to the ventral body-wall. Butler also shows that the 
position of the kidneys and gonads in relation to the horizontal 
membrane, is no proof of the septal nature of the latter; for the 
kidneys are entirely excluded from the ccelom in crocodiles, birds, 
chelonians, and sometimes in lizards, while they lie well within 
the body-cavity in the Amphisbeenide; and in Monitor niloticus 
the posterior part of these organs lies within, and the anterior 
portion without, the peritoneal cavity. That part of the septum 
which shuts off the lungs from the abdominal cavity is, however, 
quite a separate structure, and appears to resemble more closely 
the condition seen in some Chelonia than in any other reptiles. 
The lungs of Varanus seem also to be so intimately connected 
with the dorsal body-wall, that all trace of a pleural cavity is lost, 
and thisagain happens in 7'’estudo (see below). Or Butler suggests 
that the exclusion of the lungs from the peritoneal cavity may 
