1889. ] THE BODY-CAVITY IN LIZARDS, ETC. 463 
the chick are fairly similar, and (p. 214) giving the résumé from 
which a quotation has already been made (p. 459). 
III. (e). On the Development of the two Parts of the Post- 
hepatic Septum of the Bird. 
We have now to refer to the developmental changes grouped 
under heads B & C (p. 496). 
First, with regard to the development of the “ oblique abdominal 
septum.” 
Ravn (op. cit. p. 140) calls by the name of ‘‘ vena-cava-falte” or 
“ plica venee cavee ” the ridge that occurs in Mammals as a backward 
continuation of the embryonic lung-substance, because through it 
the vena cava inferior passes on its way from the kidneys to the liver 
and heart. But it will be seen on reference to the Plates, figs. 5 & 6, 
which together with fig. 7 show three sections of a chick of 7th day’, 
that there is a horizontal ridge of the same nature on the left side 
also (y, y), where of course there is no vena cava inferior. 
Later stages in the development of this septum are shown in the 
series of transverse sections of embryo of 10th day (figs. 20, 21, 
22, y, y), and in the transverse sections of 12th day (figs. 27 & 28, 
Say pe 
It will be seen that the growth of the abdominal air-sacs has 
considerable influence on the development of this septum, into which 
they extend from its outer anterior border. We may say in fact 
that though a starting-point is supplied by the ridge (y) which is 
visible as a backward continuation of the pulmonary mesoblast in 
the earliest stages, it is only when the abdominal air-sacs have 
attained some degree of development (as at about the time of the 
completion of the avian diaphragm, 9th to 10th days), that a true 
septum reaching from the lateral walls to the median vertical 
mesentery (cf. fig. 22, y, y) is apparent and begins to extend 
posteriorly and obliquely ventralwards. 
This oblique abdominal septum, or anterior and dorsal portion of 
the post-hepatic septum, is shown in its adult relations in figures 45 
and 46, y, y (transverse sections). 
The ventral part of the latter is formed by the laterally extended 
ventral ligament of the gizzard and hinder part of liver, which goes 
by the names of gastrohepatic ligament and the great omentum. 
We sce this membrane in the longitudinal-vertical section of 10th 
day (taken to the right of the middle line, wherefore the gizzard 
does not appear) (fig. 18, @) extending from the ventral body-wall 
to the posterior side of the liver. It is shown also in figs. 13, 17, 
19, 20, 26, 27, 28, and also in 29, GB, (3. Further, I would call 
attention to fig. 16, which is a longitudinal-horizontal section through 
the more dorsal part of the gall-bladder (¢.g) and the antero-ventral 
corner of the lung (pul.) of a chick of the 12th day. On the right 
1 Owing to the curvature of the embryo at that date, these are partly horizontal- 
longitudinal and partly transverse. They are very similar to figures 581 and 
582 in Duyal’s Atlas; but the latter fail to show the presence of the ridge 
on the left side. 
