188 EVOLUTION AND GENETICS 



thumb and great toe more or less opposable to the remaining 

 digits. Such structures are effective in the plantigrade position 

 for walking but are especially fitted for locomotion in trees. In- 

 stead of claws or hoofs they have nails. They are further char- 

 acterized by having the body covered with hair except the palms, 

 soles and parts of the face; the mammae are reduced to a single 

 pectoral pair, the eyes directed forward and the orbit surrounded 

 by bone, a clavicle always present, and the brain relatively large 

 and well convoluted. The body of every individual verifies man's 

 possession of most of these characters. 



Classification. Classifications of the Primates differ. The fol- 

 lowing is that of W. K. Gregory, which has been widely used. 

 Recent publications dealing with the phylogcny of the group do 

 not agree with it in detail, but as an indication of the general sub- 

 divisions it is wholly adequate: 



Suborder 1. Lemuroidea. Lemurs or "half-apes." 

 Suborder 2. Anthropoidea. 



Series 1. Platyrrhini. New World apes. 

 Family 1. Hapalidae. Marmosets. 



Family 2. Cebidae. Capuchins, howler monkeys, spider 

 monkeys, etc. 

 Series 2. Catarrhini. Old World apes and monkeys. 

 Family 3. Cercopithecidae. Monkeys, baboons, ma- 

 caques, etc. 

 Family 4. Simiidae. Man-like or anthropoid apes. 

 Family 5. Hominidae. Man. 



The series Platyrrhini is distinguished by a broad nasal septum, 

 a reduced and non-opposable thumb, and other characters. In 

 contrast, the Catarrhini have a narrow nasal septum, and as the 

 name suggests, the nostrils point downward. They have thirty- 

 two teeth, opposable thumb, and non-prehensile tail, which is often 

 rudimentary and not developed as an external appendage. The 

 latter group corresponds in these things with the structures of 

 man but the two lower families differ from man in the opposable 

 great toe. In general, then, man harmonizes closely in structure 

 with the other members of the Catarrhini. The differences which 

 exist are traceal)le almost entirely to differences in habits, since 

 man is an erect terrestrial species while the others are arboreal, 

 and at the most only semi-erect. 



