THE FROG AND VERTEBRATES IN GENERAL 163 



proboscis, of the Elephant, as well as the tusks which are modified, 

 greatly enlarged incisor teeth. Among the outstanding structural 

 features of economic importance are the character of the flesh 

 of certain species which makes it desirable for human consumption ; 

 the character of the skin (as in Cattle) which makes it suitable to 

 tan for leather ; and, finally, the development of mammary glands 

 which provide a supply of milk — an almost indispensable article 

 of human food which is the basis of the very important dairy 

 industry. (W. f. 92.) 



Order 9. Primates. This final order of Mammals, to which Man 

 belongs, is primarily characterized by the great development of 

 the brain — a feature generally regarded as being of sufficient 

 importance to make it necessary to place this group as the high- 

 est order of the Mammals, even though in certain other features, 

 such as the development of the muscular tissue, character of teeth, 

 and condition of young at birth, the species included are less ad- 

 vanced than certain other orders, particularly the Ungulates. Other 

 primate features are noted in the digits of the hand and foot, which 

 bear nails rather than claws or hoofs, and also in that the first 

 digits (toe or thumb) are opposable (one or both) to the other digits. 

 The primate appendages are primarily adapted for grasping, a 

 function which corresponds to the arboreal habitat of the great 

 majority of species. 



The Primates are divided into two suborders on the basis of a 

 comparatively minor structural feature, namely, the separation or 

 contact of the front teeth in the anterior median line. Thus in 

 the suborder Lemuroidea the teeth are separated, while in the 

 suborder Anthropoidea the teeth are in contact. The Lemurs 

 and Marmosets, which belong to the Lemuroidea, are rather small- 

 sized quadrupeds with a comparatively long tail. The long- 

 nosed lemur face is not unlike that found in certain of the lower 

 Mammals. The Marmosets are climbers, and it is interesting to 

 note that there are claws on certain digits. (W. f. 93.) 



The Anthropoidea includes all the remaining Primates, such as 

 the long-tailed Monkeys of which there are numerous species found 

 in South America and various regions in the Old World ; and the 

 short-tailed Anthropoid Apes, represented by the Gibbon, Orang- 

 utan, Chimpanzee, and the rare Gorilla. Finally, Man is classi- 

 fied as a separate family (Hominidae) of the Anthropoidea. Only 

 one species {Homo sapiens) is recognized at present. The Anthro- 



