1908.] AXTECHINOMYS A.ND OTHER MARSUPIALS. 593 



exception *). A slight modification of this stage is seen in many 

 Cai'nivora and in the Primate Chrysothrix, where the intestine 

 can be laid out flat without tearing the mesenteries ; this is 

 achieved by the reduction of the ligaxnentum cavoduodenale, and 

 it is possible that the entire disappearance of this mesentery may 

 account for such cases as Ce/itetes, which therefore show an unreal 

 primitiveness diie to a reversion by degeneration. 



This stage may be subdivided into two ; of which one, 

 Stage II. A, will include those forms in which the intestine is merely 

 folded over once without further specialisation, and will inchide 

 some Marsupials (e, g. Dklelj^hys, Hypsiprymnus), Edentates (e. g. 

 Dasypus), Carnivora (? all genera), Lemurs (e. g. Microcehus) ; and 

 Stage II. B, which will be characterised by the further specialisation 

 caused by the attachment to the colon of the omentum :*this 

 second group -wdll contain many Marsupials (e. g. Macroptis), 

 Edentata (Oi^ycterojncs), Primates (division of Anthropoidea 

 without exception). 



Text-fiff. 122. 



Diagram of Mammalian gut, Stage II. A. 

 O. Omentum. Si. Small intestine. Other letters as in text-fig. 120. 



In Stage III. the essential difference from the two earlier 

 stages is the formation of fixed permanent loops of the colon, 

 termed ansce coli. Combined with this is always an intestine 



* Klaatscli's figure {Joe. ei#. fig. 12, p. 671) of the young IfopaZe with an ansa coli 

 absent in the adult (fig. 13, p. 672) suggests the possibilitj^ of the Primate simplicity 

 being due to reversion. 



38* 



