The geographical distribution of animals, with a study of the relations ...

chap, iv.] ZOOLOGICAL KEGIONS. 51or a group of animals, is a matter of the first importance ; and,as regards the general history of life upon the globe, may beconsidered to be one of its essential characters. The structure,affinities, and habits of a species, now form only a part of itsnatural history. We require also to know its exact range atthe present day and in prehistoric times, and to have someknowledge of its geological age, the place of its earliest appearanceon the globe, and of the various extinct forms most nearlyallied to it. To those who accept the theory of development asworked out by Mr. Darwin, and the views as to the generalpermanence and immense antiquity of the great continentsandoceans so ably developed by Sir Charles Lyell, it ceases to be amatter of surprise that the tropics of Africa, Asia,and Americashould differ in their productions, but rather that they shouldhave anything in common.Their similarity, not their diversity,is the fact that must frequently puzzles us.The more accurate knowledge we have of late years obtainedof the productions of many remote regions, combined with thegreater approaches that have been made to a naturalclassificationof the higher animals, has shown, that every continent orwell-marked division of a continent, every archipelago andeven every island, presents problems of more or less complexityto the student of the geographical distribution of animals. Ifwe take up the subject from the zoological side, and study anyfamily, order, or even extensive genus, we are almost sure tomeet with some anomalies either in the present or pastdistributionof the various forms. Let us adduce a few examples ofthese problems.Deer have a wonderfully wide range, over the whole of Europe,Asia, and North and South America ;yet in Africa south ofthe great desert there are none.Bears range over the whole ofEurope, Asia, and North America, and true pigs of the genusSus, over all Europe and Asia and as far as New Guinea ;yetboth bears and pigs, like deer, are absent from Tropical andSouth Africa.Again, the West Indian islands possess very few Mammalia,all of small size and allied to those of America, except oneBOSTON UNIVERSITY~'COLLEGE Or r*Al ARTS