1902. J ADAPTATIONS IN DIPROTODONT MARSUPIALS. 15 



whom I fully agree, it may be asked — why has, then, the small 

 intestine become lengthened in the three phyllophagous animals ? 

 I think that this may be explained in the following way : — The 

 leaves of which the food of the animals is composed consist not 

 only of cellulose, but contain also protoplasmic, amylaceous, and 

 other substances, which ought to be digested and re-absorbed in 

 the small intestine. These substances are, however, all of them 

 enclosed within the membranes of the cellules of the leaves, and 

 these membranes are more resistant than, for instance, the thin- 

 waUed cellules composing the pulp of fruit. The food derived 

 from leaves must consequently be subjected to a longer treatment 

 also in the small intestine, before yielding its useful substances, 

 than food consisting of fruits needs — not to speak of animal food. 

 The small intestine of Trichosurus is villous, as has already 

 been remarked by Oppel \ bvit my material does not allow any 

 description of the villi. About 93 cm, from the opening into the 

 large intestine I have found two roundish Peyer's patches, 

 situated near each other and measuring respectively 3 and 

 2| mm. in diameter. They are solid and not composed of small 

 nodviles. In the intestine of the Koala there are no Peyer's 

 patches according to Forbes {I. c. p. 184). The last portion of 

 the ileum is in Trichosxirus conspicuously more thick- walled than 

 other parts of the small intestine. Its mucous membrane forms 

 distinct longitudinal plicse, and it seems thus to be more rich in 

 glands than other parts. In addition to this there are to be 

 seen what I am inclined to term, with Owen, some " wide and 

 deep glandular fossse." The largest of these is situated about 

 1 cm, from the ileo-csecal opening, and measures nearly 5 mm. in 

 length by 1^ in width. About 1 cm. higher up the ileum there 

 is another one of the same kind although smaller, so that it 

 measures only 2 mm. in length. There are also indications of 

 some other depressions, but they are shallower and less distinct. 

 My material does not allow of any histological investigations, but 

 I hardly think I can be much wrong in interpreting these as 

 accumulations of glands. The "fossfe" mentioned by Owen in 

 the words quoted above were found by him in the large intestine 

 of the Koala, and are thus not homologous with these. The 

 " fossee " found by Owen have, however, their homologue in a 

 thickened glandular area, with numerous shallow depressions, 

 situated on the adjoining borders of the colon and the Cfecum 

 of Trichosurus just opposite the ileo-csecal opening. The ileo- 

 csecal valve is well developed and protrudes into the colon. The 

 limit between the colon and the ceecum is only marked by a short 

 plica from the ileo-cfecal valve and a weak sphincter cceco-colicus. 

 If this sphincter is weak it is assisted in its functions by a series 

 of cEBcal sphincters which are strongly developed. Their number 

 is four. The first is situated about 3 cm. from the cseco-colic 

 one. The next is stronger and found at about the same 



1 'Lehrbiich d. vergl. mikvoskopischen Aiiatomie der Wirbeltiere,' Zweiter 

 Teil (Jena, 1897), p. 288. 



