54 THE PHYSICAL KINSHIP 



from which existing forms were evolved were 

 dispersed over the earth at a time when physio- 

 graphic conditions were very different from what 

 they are now, that it is possible to account for the 

 peculiar manner in which animals are distributed 

 over the earth. The cassowary is a flightless bird 

 of the ostrich order inhabiting Australia and the 

 islands to the north of it. This bird is found no- 

 where else in the world, and each area has its own 

 particular species. The same things are also true 

 of the kangaroo. It is found over a similar region, 

 with a different species occupying each land mass. 

 Now, on the hypothesis of special creation there 

 is no thinkable reason why these animals should 

 be divided, as they are, into distinct species, and 

 restricted to this particular region. But on the 

 hypothesis of evolution it is perfectly plain. All 

 of these regions at one time were united with one 

 another, and were subsequently submerged in part, 

 forming islands. Each group of animals, being 

 isolated from every other group and subjected to 

 somewhat different conditions, developed a style 

 of departure from' the original type of structure 

 different from that of every other group in response 

 to the peculiar conditions operating upon it. This 

 has led, in the course of centuries of selection, to 

 the formation of distinct species such as exist 

 to-day. 



Lombock Strait, a narrow neck of water between 

 Bali and Lombock Island, and Macassar Strait, 

 separating Celebes from Borneo, are parts of a 

 continuous passage of water which in remote times 



