1888.] ANAIOMY OK THE LACERTILIA. 103 



statements in this way, unless, indeed, the last half of the sentence 

 from Hoffmann, quoted above, may be held to imply that the luns^s 

 are shut off from the abdominal cavity by a membranous partition. 

 I should myself consider that these words only refer to the reflected 

 layer of peritoneum which covers each lung ; this is, of course, quite 

 a different thing from the horizontal membrane in Varanus, which 

 shuts off both lungs from the abdominal cavity. 



I find, however, in an account of the dissection of a Monitor 

 published in the very first volume of the ' Proceedings ' ' of this 

 Society, by Dr. Martin, a couple of sentences which in all probabiUty 

 do refer to tiiis structure, which, so far as ray experience goes, is 

 so highly characteristic of the Monitor Lizards and of that group 

 only. The author writes : " the chest is divided from the abdomen 

 by a partial membranous diaphragm attached to the parietes of the 



abdomen b}' numerous strings or filaments the liver lies in 



the abdominal cavity just below the diaphragm." There is, however, 

 no further remark concerning the structure in question ; it is not 

 emphasized as a peculiarity of the Monitor nor is it compared in any 

 way with what I believe to be an homologous structure in the 

 Crocodilia. 



This horizontal septum closely resembles a structure in the Croco- 

 dilia (fig. 3) which has been described by Prof. Huxley'"^ as well as by 

 others : this consists of a membrane, partly muscular, which is 

 attached to the pubis and to the abdominal parietes behind, and in 

 the median dorsal line to the backbone ; it entirely envelopes the coils 

 of the intestines, so that they are not visible when the body-wall is 

 cut through. Anteriorly this muscular expansion is attached to the 

 fibrous compartments in which are lodged the stomach and the two 

 lobes of the liver ; the lungs are thus shut off from the abdominal 

 cavity ; this membrane bears on the ventral surface the anterior 

 abdominal veins : there is evidently a close similarity, so far, between 

 the Crocodile and the Lizard ; furthermore in both animals the 

 lateral regions of the membrane are connected with the lateral 

 parietes by fibrous bands, and in both the fat-body lies outside of the 

 membrane and outside of the abdominal cavity ; the reproductive 

 glands and the kidneys have a similar relation to the membrane in 

 both types ; in the Crocodile as in the Lizard the reproductive 

 glands and the kidneys are separated by the membrane ; the former 

 lie within, the latter without, the abdominal cavity. The only 

 differences are that in the Crocodile the membrane is largely covered 

 by muscular tissue, and that instead of simply passing over the liver 

 and stomach, it becomes connected with special sheaths enveloping 

 these several organs. In these points the Crocodile, as Prof. Huxley 

 has pointed out, resembles birds. 



The above considerations point, in my opinion, to an unmistakable 

 resemblance between tlie Monitor Lizards and the higher Sauropsida, 

 a resemblance which is, perhaps, a little unexpected. There has 

 never, so far as I am aware, been any doubt as to the thoroughly 

 Lacertilian nature of the Varanidie ; in all the schemes of classitica- 

 P. Z. S. 1831, p. 138. ' P. Z. S. 1882, p. 568. 



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