Evolution 



and the hemispheres show little if any tendency to develop those 

 wrinkles and fissures which always accompany the higher type 

 of intelligence. Probably the most primitive member of the 

 whole group is the Centetes from Madagascar, shown in Fig. 119. 

 The hedgehog and the shrews are its best-known examples. 

 An interesting point regarding the hedgehog is that, like few 

 other mammals, it has persisted almost unchanged from early 

 tertiary times. It is thus to be regarded as a very antique type, 

 not only in its main features, but in its details. 



The Lemurs are an interesting group, standing, as they do, 

 midway between the primitive placental forms and the monkeys. 

 Their special home, as already mentioned, is Madagascar, to 

 which some thirty-six of the fifty known species are confined, but 

 they occur also in Africa and in South-Eastern Asia. They are 

 arboreal and mostly nocturnal in habits, and their food consists 

 partly of fruit, etc., partly of insects. They were formerly much 

 more widely distributed, and many fossils have been unearthed, 

 for example, in North America. They show certain characters 

 of a distinctly primitive kind, such, for instance, as their habit of 

 hibernation. Their typical number of teeth is thirty-six, the same 

 as in the lower monkeys, but fossil forms are known which possessed 

 the full number of forty-four. 



In their general build they show marked adaptation to their 

 arboreal life, and approach, some more and some less, the appear- 

 ance of the monkeys. The fore-limbs are considerably modified 

 from the condition in which they occur in ordinary mammals, in 

 which they are placed vertically under -the body. They are 

 placed in a more lateral position, so that they can be moved 

 through greater angles, and extended over the head. In common 

 language, they are ceasing to be legs, and are becoming arms. As 

 in the monkeys, the thumb and the great toe are opposed to the 

 other digits so as to render the hand and foot more efficient as 

 grasping organs. Hence the Lemurs may be included with the 

 apes as ' Quadrumana,' or four-handed animals. The fingers 

 and toes either bear claws, as in the lower animals, or flattened 

 nails like those of the higher apes and man, many species possessing 



138 



