1889.] FAT-BODIES OF THE SAXJROPSIDA. 607 



lie in distinct spaces beneath the skin, separated from the abdominal 

 cavity by a stout muscular tract, are not the homologues of the 

 subperitoneal fat-bodies of the Monitors, .but of subcutaneous fat- 

 deposits occurring in the Sauropsida in addition to the subperitoneal 

 (c/'. p. 609). The fat-bodies of the Crocodiles that correspond to 

 those of Lizards are more lateral than is usual in the latter group. 



Thus the membrane that is referred to by Beddard as being 

 muscular in the Crocodile, according to the view here expressed 

 represents, in the ventral region, a great part of the muscular body- 

 wall. 



In the quotations given above the position of the kidneys relatively 

 to the so-called " horizontal membrane " has been referred to. A 

 reference to figs. 14 and 15 shows that in Monitor niloticus the 

 hinder portion of the kidney projects well into the peritoneal cavity 

 which contains the intestines and reproductive glands, and that the 

 part in front of this lies as it were in the membrane in question, or 

 between its peritoneal and parietal layers ; so that, though the anterior 

 portions of the kidneys project outwards into the circumadiposal 

 cavities, the membrane referred to does not exactly separate these 

 from the reproductive glands. 



But, even if the whole of the kidney were shut out of the general 

 intestinal cavity, this would, I think, neither be a point of special 

 similarity to the Crocodiles nor have much morphological signifi- 

 cance. We find such a condition not only in the Crocodiles but in 

 Chelonia (Emys, Testudo). In Snakes {cf. figs. 8, 9, 10), and in 

 the Lizards themselves, the extent lo which the kidneys project into 

 the peritoneal cavity is variable, and the Amphisbsenidse are, so far 

 as I know, unique in the freedom with which these organs hang 

 into the peritoneal cavity. 



In birds, again, the kidneys, as opposed to the reproductive glands, 

 are extra-peritoneal in position {cf. figs. 46 and 47 of my paper " On 

 the Subdivision of the Body-cavity," Plate XLIX. above, p. 452). 



I think that the preceding points to the conclusion that the 

 membrane which in Monitors is seen to cover the abdominal viscera 

 when the body-wall is first cut into, must be regarded as the perito- 

 neum, backed by the lining membrane of the space into which the fat- 

 bodies project — that it, in fact, consists of the peritoneum together 

 with another layer belonging to the body-wall. 



With regard to the term " liorizontaV membrane or septum it 

 seems to me that it is used to comprise two things, which may with 

 advantage be considered apart. There is, firstly, the membrane, 

 refeired to above, which divides the circumadiposal and peritoneal 

 cavities. To this I would attach no particular morphological impor- 

 tance. It appears to me not to divide one part of the body-cavity 

 proper from another, but to be, as Beddard (1, p. 100) seems fully to 

 recognize, but a special development of a tract which occurs in other 

 Lizards, correlated, as I would say, in Monitors with the greater 

 extension of the circumadiposal spaces, In fact, in the separation 

 of the membrane under discussion from the body-wall, the Monitors 

 seem to be but following what is a line of weakness for Reptiles 



