1889. | THE BODY-CAVITY IN LIZARDS, ETC. 453 
Nothing appears to be known of the development of the subdivisions 
of the body-cavity in the Crocodile, and to treat the subject of this 
paper satisfactorily the writer should have a familiar and personal 
acquaintance with not only that, but with the whole corresponding 
course of development, in Mammal, Bird, and Lizard, so far as 
the partial or complete septa in the body-cavity are concerned. 
I have followed the development in the chick down to the twelfth 
day by means of complete series of consecutive sections taken in 
different planes, and particularly during the latter half of this period ; 
but I cannot pretend to an equal acquaintance with the development 
in Mammalia, and in common, as I believe, with other observers, I 
have not been able, in the case of the Lizards, to compare the develop- 
ment in Varanide or Tetide with that in Lacertide. 
Nevertheless it may be well at the present stage to make known 
in a preliminary paper certain observed facts, and to indicate certain 
homologies which they suggest. 
I append a list of the more noticeable of the papers bearing on 
this subject to which I have referred; but, while acknowledging 
indebtedness to the authors of the same, I do not attempt a résumé 
of their contents ; but, except in those cases where reference is made to 
any of them, confine myself to sketching the facts from my own 
observation, and to stating the conclusions to which they appear to 
point. 
Certain subjects, such as the later stages in the development of 
the Avian diaphragm, and the formation of the air-sacs, as from 
the sixth to the twelfth day of incubation in the Fowl, and the rela- 
tions and homologies of the various ligaments and septa about the 
liver-lobes in Birds and Reptiles, do not seem previously to have 
received full attention. 
The consideration of these and of certain other points seems to 
show that the complication of the membranes in the adult Bird and 
Crocodile can, to a greater extent than might be imagined, be analyzed 
and expressed in terms of structures found in other Reptiles, where 
the arrangement is simpler. 
II. On THE SUBDIVISION OF THE Bopy-CAVITY 
IN THE ADULT FowL. 
On carefully cutting away the sternum and ventral body-wall of a 
Duck or Fowl, we see that the liver-lobes for the most part lie in two 
sacs entirely shut off from the rest of the body-cavity (cf. Plates 
XLVIII. and XLIX. figs. 29 and 44-47, 4, h'; 1, 1'). These sacs 
are bounded ventrally by the sternum, externally by the vertical 
portion of the ‘ oblique septum ” of Huxley (s.00.), mesially by the 
median ventral ligament (m) and posteriorly by the “ omentum ” 
((), which passes anteriorly into the hinder portion of a transverse 
septum (vy) ventral to the abdominal air-sacs*. Not much, however, 
1 Huxley appears to me to have included this transverse septum (y) in his 
“ oblique septum,” while Perrault appears to have described the two elements /3 
and y (just referred to separately, by reason of their arising quite separately in 
the embryo) as the “diaphragme transversal.” Sappey (1, p. 35) says, speaking of 
