1908.] ANTECHINOMYS AND OTHER MARSUPIALS. 571 



represented as different. I am disposed to believe from its 

 .shortness that the gut of Bradypus will be found also to conform 

 to this plan *. The simple colon of all these forms of moderate 

 length, neither excessively long nor excessively reduced, is, as I 

 think, in agreement Avith Dr. Mitchell, a mark of low position 

 in the series, especially since no modification traceable to different 

 feeding-habits is recognisable. 



On a superficial inspection the intestinal tract of many 

 Carnivora appears to be constituted on the same simple plan 

 as that of Antechinomys, Myrinecopliaga, Centetes, &c. That is 

 to say, the gut can be laid out in one continuous coil without 

 removing it from the body or cutting any mesentery. There are, 

 however, variations in the degree of freedom of the gut. In 

 Cercoleptes caudivolvidus for example, the gut can be readily laid 

 out either to the left or to the right, and then forms a continuous 

 coil apparently with a continuous mesentery throughout. It 

 would seem in fact to have retained the primitive arrangement 

 altogether. In Ictonyx ccqjensis, on the other hand, this spreading 

 out into a continuous fold is only possible on the left side ; the 

 gut cannot be thus spread out on the right side. So too with 

 Nandiivia hlnotata. In Ursus syriacus the gut can be readily 

 laid out on the left side ; but I have unfortunately no note as 

 to whether it can be also spread out to the right so as to present 

 the appearance of a continuous mesentery like that of the simplest 

 mammals. In Genetta ruhiginosa, however, the gut can, as in 

 Cercolejytes, be laid out on either side of the middle line without 

 tearing or unduly stretching any mesenteries. The disposition 

 of the gut, however, in these animals, though superficially as 

 has been said that of the simplest forms in the order, is in reality 

 diflferent. It will be seen that where the end of the duodenal 

 loop comes near to the middle dorsal line, it is actually fastened 

 to the mesocolon by a short mesentery, as is shown in the 

 accompanying figure (text-fig. 120 B on p. 591). The comparative 

 freedom which the whole intestinal tract enjoys is clearly due to the 

 partial disappeai^ance of this particular mesentery, the ligamentum 

 cavo-duodenale. If more extensive, the arrangement of the 

 intestine in a continuous coiled line from stomach to rectum 

 would be impossible. If, on the other hand, the mesentery 

 disappeared altogether, there would be actually a continuous 

 mesentery from end to end of the gut, I am inclined, therefore, 

 to believe that the intestine has in these forms undergone a. 

 simplification approximating to the primitive state of the 

 gut with its mesentery. And indeed it may well be that even 

 the apparently simple forms like Ardechinomys are in reality 

 the terminal stage in such a reduction, and not evidence of the 

 persistence of a primitive state of affairs. I believe, however, 

 that the coincidence of this apparently primitive state in such 

 widely removed types as Centetes and Tamandua is evidence in 



* As to OTiolcepus, however, Klaatsch observes that " das Lig. hepatocavoduodenale 

 ist schwach entwickelt." 



