24 CHAPTERS ON EVOLUTION. 



than those included within the sphere of this third division of biology. 

 Why, for instance, are kangaroos and animals of like grade only 

 found in Australia and adjacent islands ? Why are the opossums 

 near relations of the kangaroos absent from the Australian home of 

 their nearest kith and kin ? and why do they occur in America, when 

 natural expectation would have placed them in Australia ? Why are 

 antelopes well-nigh confined to Africa, which has no true deer, 

 whilst the deers are otherwise world- wide in their distribution ? Why 

 are humming-birds only found in the New World, over the length 

 and breadth of which they are widely distributed ? Why are the 

 monkeys of America absolutely different from those of the Old 

 World ? and why are those found in Madagascar, in turn, so varied 

 from their neighbours of Asia and Africa? Why are sloths and 

 armadillos only found in South America ? Such are a very few of 

 the queries which Distribution asks, and to which this science endea- 

 vours to supply an answer. 



We thus perceive, clearly enough, that the situation and position 

 of an animal or plant on the surface of the earth is no mere matter of 

 chance, but is as much the result of law, and has been as clearly 

 brought about by the circumstances which regulate existence as a 

 whole, as its structure is the result of laws of development acting in 

 definite fashion and ordered sequence. Distribution, it is true, is a 

 biological science as yet in its infancy. It presents us, we may note, 

 with two aspects, under one of which we settle the place and position 

 of an animal in space, that is, in the world as it now exists such is 

 Geographical Distribution. Through the other aspect of this science, 

 we determine, by the aid of the history of fossils, whether it had an 

 existence in the past history of our earth, and if so, under what 

 conditions it lived. This latter phase of the subject is named 

 Geological Distribution, or distribution in time. The importance of 

 distribution as a branch of biology grows and increases daily, as we 

 perceive that the answers to many puzzles and problems of life are 

 bound up in the replies we are able to furnish to the question, 

 "Where is the animal (or plant) found ?" 



At this stage of biological investigation many naturalists might be 

 tempted to call a halt Having ascertained, as fully as may be, the 

 structure, physiology, and distribution of an animal or plant, the 

 investigation of the living form might be regarded as complete. 

 Contrariwise, however, the tendency of the biology of past years has 

 been to lay increasing stress on a fourth inquiry concerning every 

 living thing namely, " How has it come to be what it is ?" Such a 

 question is tantamount to the inquiry, " How and why was the living 

 being created so ? " an interrogation which, even a few years back, 

 would have sounded as an attempt to probe the mystery of divine 

 intent, and which, as such, would have been relegated to the domain 



