INTESTINAL TRACT OP MAMMALS. 449 



Family Epaxorthid-e. 

 I have not been able to examine any example of this family 



Sub-Order DIPROTODONTIA. 



Family Phascolarctid^e. 



I have not been able to examine a Koala or a Wombat. Flower (5), however, has 

 described the alimentary canal of Pltascolomys, and has figured the caecum, the figure 

 being reproduced by Oppel (16, p. 567). According to him, the whole intestinal tract 

 is long, in relation to the vegetable food, and the hind-gut is longer and more 

 voluminous than the fore-gut. The proximal portion of the colon is sacculated, and 

 Flower identifies as the true caecum a forwardly projecting, wide, but short, sac of the 

 colon. In addition to this, however, he figures and describes a second caecum, larger 

 than the first, but very narrow and vermiform, although provided with a separate 

 aperture into the colon. The most obvious interpretation of the structure is that the 

 Wombat has a pair of caeca, each member of which is degenerating, the normal caecum 

 being short and thin-walled, the second member of the pair being elongated and 

 probably glandular. It has been repeatedly referred to as the vermiform appendix of 

 the Wombat, but it is obviously not that portion of the normal caecum. 



Family Phalangerid^e. Phalangista vulpina (fig. 6, p. 450), Dromicia nana, 

 Petaurus sciureus (fig. 47, II, p. 518), Bettongia penicillata (fig. 7, p. 451), 

 Bettongia cuniculus, Petrogale penicillata, Macropus bennetti (fig. 8, p. 452) 



I follow Weber (27) in not attempting to separate the Phalangers from the 

 Kangaroos. 



In Phalangista vulpina (fig. 6) the duodenum is hardly separated as a specialised 

 loop. Meckel's tract is relatively short, occupying only part of the circumference of 

 a circle. The caecum is extremely long and wide, and passes directly into the hind- 

 gut, the straight termination of Meckel's tract entering the continuous caecum and 

 hind-gut almost at a right angle. The hind-gut shows a very definite colon subdivided 

 into a series of minor loops, whilst the rectal portion is short and straight. The 

 anterior mesenteric vein appears to have as its chief tributary the large caecal vessel, 

 whilst it receives minor tributaries from the duodenum and from Meckel's tract, and is 

 joined by a large vessel which represents the colic branch and the posterior mesenteric 

 or rectal vessel. It is plain that the primitive simplicity of the portal system has been 

 distorted in appearance by the disproportionate growth of the caecum and the colon, 

 but the underlying type is not dissimilar to that in Didelphys and the Polyprotodonts. 

 The intestinal pattern in Dromicia is essentially similar, but Meckel's tract is more 

 nearly circular, and the hind-gut is much shorter and very wide, with the result that 

 the colon is represented by a single wide loop. The condition in Petaurus resembles 



