_Most probable view of the general process_--Last great period of change was the Glacial epoch--This, therefore, is the key to geographical distribution--Condition of things during the Glacial epoch---In America--Changes in temperature--In physical geography and in species--In Europe--Application of principles 196 (1) _Australia_--Characteristics of its fauna--Explanation of--Isolation very early--Position of marsupials and monotremes in the Taxonomic scale--Australia isolated before the Tertiary--Effect of competition on evolution 200 (2) _Africa_--African region defined--Two groups of its mammals, indigenes, and invaders--Effect of the invasion 204 (3) _Madagascar_--Characteristics of its fauna--Relation to African indigenes--Separated before the invasion-- Significance of its lemurs 205 (4) _Island life_--Two kinds of islands--Defined and illustrated by examples--(_a_) _Continental islands_-- General character of fauna--Illustrated by Madagascar, New Zealand, British Islands, coast-islands of California --Characteristics of the faunas of these explained--(b) _Oceanic Islands_--Defined--Characteristics of faunas and their origin 207 (5) _Alpine species_--Characteristics of and their origin explained--Migrations of Arctic species during Glacial times, and their isolation on mountains 215 _Objection_--Mode of change of species on borders of ranges-- Examples--Sweet-gum--Sequoia 217 _Answer_--Distribution of these forms in time, and their migrations--They are remnants--Intermediate forms are extinct 219 CHAPTER IX. PROOFS FROM VARIATION OF ORGANIC FORMS, ARTIFICIAL AND NATURAL. _Limitation of the use of experiment in morphology_--Unconscious experiments in breeding, and their results--Principles involved--Inheritance, immediate and ancestral--Effect of true breeding long continued--Method of selection illustrated by diagram--Formation of a race--Process the same in nature --Show selective effect of physical environment--Of organic environment--Of migrations--Of unlimited time--Other factors of change, and their effects shown in nature and in domestication--Differences between artificial and natural species 222 _First difference, reversion_--The tendency to reversion described--The reason explained--Illustrated by the case of the pointer 229 _Second difference, intermediate forms_--Reason is, these are eliminated in nature 232