IXTESTIXAL TRACT OV MAMMALS. 



249 



divergence from the primitive type, but this would not affect the 

 position of the caecum, and quite certainly the gut-pattern offers 

 110 argument for any close association between Chiroptera and 

 Insectivora. 



The gut-pattern of Carnivores, notwithstanding the enormous 

 lengthening of the fore-gufc in the Fissipedia, has moved little 

 from the primitive type, consisting of a fore-gut developed from 

 the greater part of the pendant loop, and a hind-gut, which, 

 although relatively short, is always longer than the length that 

 it has to traverse and not infrequently presents an expansion 

 that may be termed an anna coli sinistra. The Bears ai'e the 

 only exception to the coherence of the picture ; they have no 

 cascum, but the anatomical relations seem to show that their 

 csecum was originally placed much more near the proximal end 

 of the recurrent limb of the pendant loop, and that the distal 

 portion of that loop has given rise to an ansa coli dextra absent 

 in the other groups. The true explanation may be that the 

 apparent simplicity of the pattern in other Carnivores has come 

 about by reduction. 



The Prosimian pattern is not far removed from the primitive 

 type, but tends to the development of at least one minor expansion 

 of the recurrent limb of the pendant loop, an ansa coli dextra, 

 which may be straight or spirally coiled, and there may also be 

 an ansa coli sinistra. 



The Simian pattern is best understood as derived from the 

 Prosimian pattern by reduction. 



If the gut-patterns were our sole source of information as 

 to the inter- relationships of existing mammals, I do not think 

 that we could get much further than is set forth in the annexed 

 table, in which little stress must be laid on the vertical 

 arrangement : — ■ 



Marsupialia. 



Xenarthra. 



Tubulidentata. 



— Pholidota, 



Monotremata. 



{Hyracoidea. 

 Sirenia. 

 Proboscidea. 



Mystacoceti — Odontoceti . 



f Hippopotamidse. 1 m . •. • i f Tylopoda. 



^ r-j • 1 r xi'asruJoiciea, ^ -w-^ 



[ buidaj. J ° [ Pecora. 



Perissodactyla, 



Prosimiee — Simiae. 



Rodentia. 



Insectivora. 



Chiroptera. 



Carnivora, 



