518 



DE. P. CHALMERS MITCHELL ON THE 



in the Capybara. A condition closely similar, but in which the facts of the case are more 

 striking, occurs in Ochotona (fig. 4G, II, p. 517), where the accessory caecum is a long 

 papilliform hollow process. Since observing this in a specimen of Ochotona rufesoens 

 that died in the Zoological Gardens, I find that it was described and figured by Pallas 

 (20) in the case of three species of what is now known as Ochotona. It is to be noticed, 

 however, that in one of the three figures (Lagomys ogotona) a third unpaired caecal diver- 

 ticulum is figured. The presence of the latter may, if confirmed as a normal occurrence, 

 throw some doubt on my interpretation of the second caecum in Ochotona as the 



Fig. 47. 



Ileo-CiTCal regions in Dasypus minutus (I), Petaurus sciureus (II), aud Gazdla mariea (III). 



S.I. Cut end of small intestine. 



H. Cut end of colon. 



C. Normal efecum. 



Ca. Second ca?curu, symmetrical in I, vestigial in II, reduced to a mass of lymphoid tissue. in III. 

 W. Edge of " window " cut into wall of gut. 

 LA. Tree tubular aperture of ileum to colon. 



IS. Dotted lines show position of flaps of ilco-cg»cal valve. 



vestigial representative of the second member of a primitive pair. In several Antelope?, 

 e. g. Gazella mariea, (fig. 47, III), the vestigial presence of a second caecum is strongly 

 suggested by the configuration of the junction of the ileum and colon and by the 

 presence of a mass of lymphoid tissue (at C2 in fig. 47, III) at the point where the second 

 member of a pair would lie. 



Comparison of the three drawings in fig. 47 will, I think, lead any anatomist to the 



