PROBLEMS OF DISTRIBUTION AND THEIR SOLUTION. 173 



continents has remained unchanged, their minor features and more 

 intimate details have been subjected to frequent disturbance. Thus 

 in the past, as at present, the uniformity of geological action postu- 

 lates the work of rivers in eroding the land, of the sea in defacing 

 the coasts, of ice in carving the land surface, and of volcanic action 

 in depressing this area or elevating that, and in causing the sea to 

 rlovv here, or to repress its march there. Professor A. Geikie maintains 

 that the stratified rocks, instead of being formed in the beds of deep 

 oceans, " have all been deposited in comparatively shallow water." 

 And, again, this eminent geologist remarks of the manner in which 

 this earth's materials have been formed, that " From all this evi- 

 dence, we may legitimately conclude that the present land of the 

 globe, though formed in great measure of marine formations, has 

 never lain under the deep sea ; but that its site must always have 

 been near land. Even its thick marine limestones," adds Professor 

 Geikie, " are the deposits of comparatively shallow water." 



Thus with the proofs of the general permanence and stability of our 

 great continents at hand, we can completely account for all the plainer 

 facts, and for many of the difficulties, of distribution. For example, 

 we infer that about the middle of the Tertiary period, Europe and 

 Asia, as at present, formed one continuous land surface, which con- 

 tained as its inhabitants the elephants, rhinoceroses, giraffes, apes, 

 and other forms now found only in the Oriental and Ethiopian 

 regions. Antelopes were then found in Southern Europe, and the 

 giraffes extended from the South of Europe to the North of India. 

 But we must likewise take account of those more intimate changes 

 of land and sea which accompanied the general permanence of the 

 continents. At the time we are considering, Africa south of the 

 Desert was a large island ; India and Ceylon were isolated by sea 

 from Asia ; Northern Africa was united to the South of Europe ; 

 Asia Minor was joined to Greece ; the outlines of the great zoolo- 

 gical regions of the Old World were, in short, actually mapped out 

 in the middle of the Tertiary period in the then existing lands and 

 seas. But neither the detached India nor the isolated Africa pos- 

 sessed the abundant quadruped life of Europe and Asia. They 

 possessed only the lower life of the Eocene time. When, however, the 

 next series of physical alterations took place, when land passages 

 arose between Europe and Asia together on the one hand, and 

 Africa and India on the other, the higher quadrupeds migrated to 

 these areas. There some adapted themselves to their new condi- 

 tions, and flourished in their new localities, whilst others succumbed 

 to the more rigorous surroundings which faced them. The ante- 

 lopes, for instance, migrating to Africa, flourished in Ethiopia, 

 because there they found a plentiful vegetation and the other condi- 

 tions of life calculated to produce the development of new species 



