INTESTINAL TRACT OV MAMMALS. 



189 



is disposed sometimes ivregulai-ly, sometimes in a spiral. The most 

 conspicuous spiral ai-raugemeiit in the mammalian gut, however, 

 the colic spiral of Ruminants, appears to be constant. 



Descriptions arranged systematically. 



Sub-Class MONOTREMATA. 

 Order Monotremata. 



I have already figured the gut-patterns of Ornithorhynchus 

 and Echidna (Mitchell, 1905, figs. 1, 2), but my material was then 

 only rather badly 23reserved spirit examples. By the kindness 

 of Dr. Colin Mackenzie, who has brought from Australia a 

 aiiagniticent set of well-preserved examjDles of Monotremes and 

 Marsupials, I have now seen several much better examples of 

 Ornithorhynchus and Echidna. The gut-patterns of these animals 

 are rather more alike one another and the general mammalian 

 type than I was formerly able to make out. 



Text-fio-ui-e 2. 



Intestinal tract of Ornithorliynclius anatinus. 



S. Cut junction with stomach. R. Distal extremity of rectum at cloaca. 

 C. Caecum. C.L. Colic loop {ansa coli dextra). 



The duodenum in each case is a well-marked loop, and is 

 attached by a cavo-duodenal ligament to the hind-gut at the 

 curved portion of the hind -gut where the recurrent limb of the 

 pendant loop bends round to join the rectal portion. Meckel's 

 tract is suspended round the circumference of an expanse of 



