464 MR. G. W. BUTLER ON THE SUBDIVISION OF [Nov. 19, 
side there is still a communication (*) between the hepatic and 
post-hepatic parts of the abdominal cavity ; and comparing this with 
figs. 15 & 17, which represent sections respectively dorsal and ventral 
to the section in fig. 16, it will be seen that the more dorsal part of 
the post-hepatic septum is composed of the oblique abdominal septum 
(y), while the more ventral part consists of the lateral “ omental” 
extension (3). On the left side the ventral and dorsal components 
of the post-hepatic septum never meet, and there is always in the 
fowl a free communication between the ‘ pulmohepatiec recess” of 
this side and the general intestinal cavity. In the duck this is 
reduced to the condition of a small aperture (ef. supra, p. 454). 
With regard to the origin of this post-hepatic septum, it would 
seem that the ventral portion (/3) is, so to speak, started by the 
vitelline veins which cause considerable inward projections of the 
lateral body-wallsin which they run. With the closing-in of the 
body-wall in the region of the umbilicus, the vessel of the left side 
which alone continues as the allantoic vein (or in the adult as an 
anterior abdominal vein carrying blood from the fat-laden omentum) 
comes to assume a more central course, but the ventro-lateral attach- 
ment of the membrane which supported these vessels persists. 
The dorsal component (y) of the post-hepatic septum, on the 
other hand, is due to the extension laterally and posteriorly, by the 
growth of the abdominal air-sacs, of the ridge that forms a backward 
coutinuation of the pulmonary tissue of either side. And it is thus 
that I believe that in those Sauropsida which have no similar arrange- 
ment of air-sacs the post-hepatic septum, which may be present 
(Crocodiles and Teiidz), is the homologue of the ventral component 
of this septum in the bird—the dorsal part being merely repre- 
sented by the membranous fold, which in many Lizards extends for 
a considerable distance behind the lungs. 
IV. On tHe Bopy-cavity oF THE LACERTILIA AND OF THE 
TEIIDZ IN PARTICULAR. 
(a) The Lacertilia generally. 
Turning now to the Lacertilia and recurring to the question of 
the ventral attachment of the lungs. The Jet lung seems to have, 
as a rule, its ventral border but slightly if at all attached, but there 
is sometimes a short ligament connecting this with the liver or tissue 
in front of that organ. 
The right lung, on the other hand, seems as a rule (ef. p. 465, 
fig. A) to have its whole ventral border attached to the dorsal 
wall of the right liver-lobe, or—seeing that dorsally it is attached 
to the middle line by another ligament—it may sometimes be rather 
described as set on the outer side of a membrane passing between 
the right liver-lobe and the dorsal part of the median mesentery. 
The spaces thus enclosed between the lung and its ligaments on the 
outside, and the cesophagus and its ligaments in the middle line, are 
homologous with the pulmohepatie recesses of birds above described 
