ii LEMURS AND THEIR YOUNG 19 



teat would of course be absolutely incomparable with a mammary 

 pouch, because in that case the wall of the teat itself would be 

 the pouch. 



Mammals belonging to quite different Orders show traces 

 more or less marked of a marsupiuni. In young Dogs the teats 

 are borne upon an area where the skin is thinner, the covering 

 of hair less dense than elsewhere all points of resemblance to 

 the inside of the pouch of a Marsupial ; in addition to this 

 there are traces of the sphincter marsupii muscle. In other 

 Carnivora there are similar vestiges. In Lemur catta a more 

 complete rudiment of a marsupial pouch is to be met with. In 

 this Lemur the teats are both inguinal and pectoral; the skin 

 in these regions is thin and but slightly hairy, and extends 

 forwards as two bands of the same thinness and smoothness on 

 each side of the densely hairy skin covering the sternum. This 

 area is sharply separated from the rest of the integument by a 

 fold which runs parallel to the longitudinal axis of the body, 

 and can be comparable with nothing save the rudiment of the 

 marsupial fold. 



One is tempted to wonder how far the habit which certain 

 Lemurs have of carrying their young across the abdomen with 

 the tail wrapped round the body of the mother is a reminiscence 

 of a marsupial pouch. 



Skeleton. 



The skeleton of the Mammalia consists almost solely of the 

 endoskeleton. It is only among the Edentata that an exo- 

 skeleton of bony plates in the skin is met with. As in other 

 Vertebrates, the skeleton is divisible into an axial portion, 

 the skull and vertebral column, and an appendicular skeleton, 

 that of the limbs. The bones of mammals are well ossified, 

 and in the adult there are but few and small tracts of cartilage 

 left. 



Vertebral Column. The vertebral column of the mammals, 

 like that of the higher Yertebrata, consists of a number of 

 separate and fully-ossified vertebrae. 



The constitution of a vertebra upon which all the usual 

 processes are marked is as follows : There is first of all the 

 body or centrum of the vertebra, a massive piece of bone shaped 

 like a disc or a cylinder. The centra of contiguous vertebrae 





