INTESTINAL TEACT OF MAMMALS. 467 



and large intestine, suggesting a primitively paired condition of the caeca. The actual 

 caecum is large, long, and wide. The hind-gut is wide in calibre and relatively very 

 long. It is thrown into a continuous series of folds in which a colon and rectum, not 

 well separated, may be distinguished. The portal system consists of an anterior 

 mesenteric vein draining Meckel's tract round which it curves, and receiving a large 

 duodenal branch. There is a strong posterior mesenteric vein, draining colon and 

 rectum. 



The pattern displayed by the Proboscidea is of primitive simplicity, consisting of 

 the duodenum, the pendent loop transformed into Meckel's tract, and a second large 

 loop forming colon and rectum. The most striking character is that the hind-gut is 

 very little shorter than the fore-gut. There is no trace of any of the special Ungulate 

 characters. Obviously this pattern is very closely similar to that of Manatus. If it 

 be remembered that the Dugong and Rhytina have only a single caecum, then it is 

 plain that in the pattern of the gut the Sirenia and Proboscidea are not far apart 

 and that neither group shows a trace of the Ungulate specialisation. 



Order CETACEA. 

 Sub-Order ODONTOCETI. 

 Family DELPHiMDiE. Phoccena communis (fig. 17, p. 468). 



This is the only example of the Cetacea of which I have been able to dissect the 

 alimentary canal myself. There is no separate duodenum, the complicated stomach 

 being immediately succeeded by an excessively long gut disposed in a series of very 

 regularly arranged coils forming an enormous mass, which tapers gradually to the 

 hind-gut. There is no distinction between the hind-gut and Meckel's tract and there 

 is no caecum. The whole length of the gut is suspended by dorso-ventral mesentery 

 stretching in almost primitive simplicity fore and aft. A single large mesenteric vein 

 runs along this, receiving, at almost diagrammatically regular intervals, a series of veins 

 from the coils. The calibre of the gut, as in most fish-eating animals, is rather small, 

 very regular throughout the length of the gut, and the wall is relatively thick. 



The simplicity of the arrangement of the gut in Phoccena appears from the recorded 

 observations to be present in at least most of the other Odontoceti, and, at first sight, 

 it would seem to be a fair interpretation that it was a primitive feature and that it 

 pointed to a separation of the Cetacea and other Mammalia before the special 

 characters of the mammalian gut had been formed. I have not myself had the 

 opportunity of examining the intestinal tract of any of the Mystacoceti, but they are 

 described as possessing both duodenal and colic loops, and a single forwardly directed 

 caecum. Moreover, in many of them the gut is relatively short, and from the 

 descriptions appears to have the normal mammalian peculiarities. I interpret the 



