CHAPTER XYI. 
SUMMARY OF THE PAST CHANGES AND GENERAL RELATIONS OF 
THE SEVERAL REGIONS. 
Having now closed our survey of tlie 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 palaeontological, 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 
