132 PERIOD V. 



n 



of the great northern land-mass of the old world, 

 and in a less degree those of North America, possess, 

 and have long possessed, of driving out the inhabitants 

 of the southern continents is one of the most important 

 factors in the peopling of the earth with new races of 

 land-plants and land-animals. Races of men, modes 

 of civilisation, religious faiths, all follow the same rule, 

 which has no doubt prevailed ever since land came to 

 predominate in the northern hemisphere and water in 

 the southern hemisphere. In the life of the sea and the 

 fresh waters no dominance of northern forms has been 

 detected. 



5. PalcBontology. — We must not claim for Darwin 

 more than a modest share in the vast extension of 

 palaeontological knowledge which the last fifty years 

 have created. A profusion of new materials has been 

 acquired by the diligence of collectors working on a 

 scale previously unattempted. But though the accu- 

 mulation of materials is the work of others, the inter- 

 pretation has been guided by the principles of Darwin. 

 The evolution of the horse has now been so fully 

 worked out that it would bear the whole weight of a 

 doctrine of descent with modification, though it could 

 not by itself reveal the process by which the modifica- 

 tion had been effected. 



Darwin on Adaptations. — The adaptation of living 

 things to their surroundings has always been a 

 favourite branch of natural history, underrated only 

 by those whose studies are little calculated to inflame 

 the curiosity. Many eminent naturalists have made the 

 interpretation of natural contrivances their chief aim. 

 Darwin equalled the best of his predecessors in accu- 

 racy, range, and ingenuity, while he surpassed them all 

 in candour. No one has done so much to vindicate the 



