CHAPTER XVI. 



SUMMARY OF THE PAST CHANGES AND GENERAL RELATIONS OF 

 THE SEVERAL REGIONS. 



Having now closed our survey of the animal life of the whole 

 earth — a survey which has necessarily been encumbered with a 

 multiplicity of detail — we proceed to summarize the general 

 conclusions at which we have arrived, with regard to the past 

 history and mutual relations of the great regions into which we 

 have divided the land surface of the globe. 



All the palseontological, no less than the geological and 

 physical evidence, at present available, points to the great land 

 masses of the Northern Hemisphere as being of immense anti- 

 quity, and as the area in which the higher forms of life were 

 developed. In going back through the long series of the Tertiary 

 formations, in Europe, Asia, and North America, we find a 

 continuous succession of vertebrate forms, including all the 

 highest types now existing or that have existed on the earth. 

 These extinct animals comprise ancestors or forerunners of 

 all the chief forms now living in the Northern Hemisphere; 

 and as we go back farther and farther into the past, we meet 

 with ancestral forms of those types also, which are now either 

 confined to, or specially characteristic of, the land masses of 

 the Southern Hemisphere. Not only do we find that elephants, 

 and rhinoceroses, and hippopotami, were once far more abundant 

 in Europe than they are now in the tropics, but we also find 

 that the apes of West Africa and Malaya, the lemurs of Mada- 

 gascar, the Edentata of Africa and South America, and the 



