THE MOUSE AND ITS ALLIES 331 



man more closely in facial appearance and in intelligence, 

 the gorilla is more man-like in the size and complexity of 

 the brain and in its habit of walking on the ground. There 

 is no reason to doubt that man's species came off from the 

 anthropoid apes ; the recent discovery, in Java, of a fossil 

 form (Pithecanthropus erectus) intermediate between man 

 and the man-like apes, is a strong additional piece of evi- 

 dence. This differentiation of man's species probably 

 began in late tertiary times. 



APPENDIX TO CHAPTER XX 



KEY TO THE ORDERS OF MAMMALIA 



Oviparous; no mammae developed . . . Monotremata 

 Young born prematurely ; reared in marsupium . Marsupalia 

 Viviparous ; no marsupium. 



hi. Teeth without enamel . . . . Edentata 



b- 2 - Teeth with enamel. 

 ci. Hind limbs absent. 



<?i. Elbow and wrist move on each other tSirenia 



(Z 2 . Fore limbs not flexible i '.." - .. Cetacea 



c%. Hind limbs present. 



di. Digits end in hoofs or hoof-like nails Ungulata 



d%. Digits end in claws. 



e\. Without hands or membranes 



between digits. 



/i. Canines absent . . Eodentia 



ft. Canines large . . . Carnivora 

 / 3 . Canines small . . . Insectivora 

 e^. Without hands ; membrane be- 

 tween digits .... Cheiroptera 

 e&. With hands .... Primates 



