1908.] 



ANTECHIXOMYS AND OTHER MARSUPIALS. 



591 



however, appears to be individual and not to pertain to the 

 species or genus ; for in another example the small intestine 

 was " normal." In another Marsupial, ^Epyprymnus rttfescens, 

 the small intestine, considerably shortei- than that of Pseudochims, 

 was also thrown into permanent coils. Here, however, I can only- 

 report upon a single individual. 



Among a considerable number of lower Mammals whose alimen- 

 tary tracts 1 have recently studied, only Dasypus vellerosus (of 

 which I have dissected a single example only) shows the same 

 fixation of the numerous coils of the small intestine. 



It is evident that this phenomenon is not a common one among 

 the Mammalia, and it is at present doubtful how far it is charac- 

 teristic, in the rare eases where it does occur, of a given species or 

 genus. 



General Considerations. 



From the foregoing considerations it is clear that we can trace 

 a number of stages of evolution of the intestinal part of the 

 alimentary tract in the various groups of Mammalia which are 

 not shown in their complete entii-ety in any one group. 



Text-fig. 120. 



A B 



A, Diagram of primitive Mammalian gut, Stage I. — B, Stage II. 

 Coe. Caecum. Cav. Lig. cavoduodenale. m. Dorsal mesentery. 



In Stage I. the intestine is suspended upon a continuous 

 mesentery and is not rotated upon itself to form the primary loop. 

 Proc. Zool. Soc— 1908, No. XXXVIII. 38 



