132 STUDIES IN LIFE AND SENSE. 



bears to the other departments of natural- history research. Taking its 

 stand as a distinct branch of inquiry ; dealing with the causes which 

 have placed animals and plants in their distinct regions ; investigiting 

 the conditions which make for or contend against the diffusion of 

 animals and plants on the surface of the globe the science of dis- 

 tribution presents problems and attempts the solution of questions 

 involving, it may be, the furthest knowledge of present and past alike, 

 which is at our command. Nor must we neglect to note that the 

 study of distribution relates that present history, in the most inti- 

 mate fashion, with the past of the globe. The continuity of the past 

 with the present is too much a ruling idea of the biological mind to 

 allow the importance of the geological factors in the world's problems 

 to be overlooked. Not a few of the knotty points of distribution are 

 soluble from the side of geology alone. If, therefore, for no other 

 reason than that it links present and past so intimately together, 

 thus making the unbroken continuity of causation a necessity in bio- 

 logical explanation, the study of distribution would take its place in 

 the first rank of the sciences of to-day. Bearing in mind this two- 

 fold division of distribution into that in space (or "geographical dis- 

 tribution ") and that in time (or "geological distribution"), we may 

 now profitably proceed to inquire into the history of the growth and 

 progress of this department of inquiry. 



If we turn to text-books on natural history, written even some ten 

 years ago, we shall discover that, whatever may be the importance 

 of the study, the science of distribution is of comparatively recent 

 growth. The information dispensed in these manuals of biology 

 resolves itself for the most part into a brief recital of the countries in 

 which different animals and plants are found. Thus the facts of dis- 

 tribution, which an intelligent child is now taught in the nursery, 

 comprehend all that was known, even in recent science, respecting the 

 habitats of animals and plants. To know that lions occur in Africa, 

 and tigers in India ; to learn that the giraffe and the hippopotamus 

 are tenants of Ethiopia, and that rhinoceroses occur both in Asia and 

 Africa ; to be able to say definitely that kangaroos never occur 

 without the bounds of Australian islands, or that humming-birds are 

 found in the New World alone ; to know where palms grow or 

 where cacti abound these were the only facts which the " distribu- 

 tion " of twenty years ago included. The plain enumeration of these 

 or any other facts, however, does not raise them to the rank of a 

 science. The mere mention of the detached countries in which 

 plants and animals occur, does not constitute a philosophical piece 

 of information calculated to explain either itself or any correlated 

 facts of natural history. That method alone converts any body of 

 details into a science, which places them in harmony with each 

 other, and which, connecting them by, it may be, even a transcen- 



