loo THE TRIUMPH OF THE MAMMALS 



came the great chill of the Chalk period and the re- 

 moval of the giant reptiles. The African branch of 

 the family now began to go ahead, while the Australian 

 branch remained nearly stationary (as isolated popu- 

 lations generally do) . Towards the end of the Chalk 

 Period, and in the next geological period, we find so' 

 rapid and rich an expansion of the mammals that it 

 is impossible to give even a summary account of it 

 here. We must be content with a simple outline. 



As I said, we do not regard the living duckmole 

 and kangaroo as ancestors of the mammals. The 

 kangaroo (and pouched animals, or ''Marsupials," 

 generally) is clearly a side-line. The duckmole is 

 a better specimen of an early ancestor, if you omit 

 the "beak" and other features which were developed 

 later. From something like the duckmole, at all 

 events, a slightly higher type of mammal, building 

 up its young in its womb, developed in Africa, and 

 travelled north. These early mammals were probably 

 "arboreal and insectivorous"; they lived in trees and 

 fed on insects. When their Golden Age dawned they 

 multiplied rapidly, and, as we have seen so often, 

 soon experienced a heavy struggle for life, and evolved 

 in different directions. From eating insects some 

 developed a taste for larger game, and the familiar 

 contest of the vegetarian and the carnivore set in. 



The development of the carnivores can be very 

 fairly traced by the rich fossil remains. Apart from 

 the seals and walruses, which retired to the ocean 



