9O THE LESSON OF EVOLUTION 



which gave rise to the Artiodactyla (pigs, camels, and 

 ruminants), and to the Perissodactyla (rhinoceros, tapir, 

 and horse). 



The Condylarthra and Creodonta are almost iden- 

 tical ; and both were plantigrade, that is, they walked 

 on the soles of their feet, and not merely on their 

 toes, as do all the Ungulates and most of the Carni- 

 vora at the present day. But in the Creodonta the 

 teeth are sharper, and the toes appear to have 

 carried sharp claws, while they are flattened in the 

 Condylarthra. The Tillodontia are the primitive 

 Rodents, which are connected by Typotlurium with 

 the Condylarthra. 



We must, therefore, suppose that the Creodonta 

 gave rise to the Carnivora, the Ungulata, and the 

 Rodentia, The Insectivora and the Creodonta pro- 

 bably had a common origin in the primitive Insecti- 

 vora ; from which stock the Lemuroidea also appears 

 to have been derived ; but as all these orders appear 

 together in the lower Eocene, their actual lines of 

 descent are doubtful. 



In the upper Eocene nearly all the existing mam- 

 malian groups are clearly separated from each other. 

 True Carnivora, true Insectivora, true Rodentia, and 

 Chiroptera (bats) appear, as also do the Cetacea. But 

 among the Carnivora there is as yet no distinction 

 between bears, dogs, hyaenas, and cats ; these were 

 only separated off in the Miocene. The Chiroptera 

 are flying insectivora. 



Of the Primates, the Lemuroidea are known in the 

 lower Eocene ; the Simiidse in the middle Miocene ; 

 where, amongst others, we find the living genus Hylo- 

 bates (gibbon). Man probably originated in the 



