conditions of the earth, those that have 

 been separated in this way will grow 

 more and more unlike. In some such 

 isolated regions there may not be much 

 change in their environment and so they 

 will change but little, if at all, and so 

 will not keep pace with those in other 

 regions where life is a constant struggle 

 with others for supremacy. It is just as 

 true in the natural world as in the com- 

 mercial, that competition is necessary 

 for the highest development. It is prob- 

 ably true that the disturbances which 

 caused the land to sink in places and so 

 disconnect what had been connected 

 lands, possibly a splitting up of one great 

 flat land mass, also brought about the 

 changes which made out of one great 

 tropical world the one that we know with 

 its frigid, temperate and tropical zones. 

 So that just at the time when the animals 

 of the different regions were separated 

 from each other forever there came these 

 changes in physical conditions which 

 would make them change to meet the 

 new conditions. But that is a long story 

 for the geologist to tell. Of course the 

 sinking of the land in different regions 

 occurred at different times, probably 

 thousands of years apart in many cases. 

 And the changes from tropical to tem- 

 perate and frigid must have been very 

 gradual also, or there would have been 

 no animals left alive in the northern and 

 southern regions. Only those near the 

 equator could have lived. 



Probably New Zealand was the first 

 considerable land mass to be separated 

 absolutely and for all time irom all other 

 land, because here we find the lowest 

 type of birds and lower animals. There 

 are no terrestrial indigenous mammals 

 even. Such birds as were not able to fly 

 across the now wide stretches of ocean 

 did not continue to develop rapidly be- 

 cause there was little change in their en- 

 vironment and because there was little 

 or no competition with other similar 

 forms. So to-day we find them either 

 very similar to what they were when their 

 island home was made an island home, or 

 else even degenerated into flightless 

 creatures. Australia seems to have been 

 the next tract of land cut off, for here, 

 too, we meet with the lower forms which 

 show the lack of the keen competition 



which their relatives further north had to 

 sustain. When North America was cut 

 off from Siberia, marking the close of 

 more or less extensive interchange of 

 communication of the animals of both 

 regions, there was little difference in their 

 animal life ; but following this separation 

 there came about a more rapid change 

 in the Orient than in the Occident. It 

 may not be quite clear why this was so, 

 but that it was cannot be doubted, for 

 some of the lower forms of animals which 

 still inhabit America have been com- 

 pletely destroyed in the Orient. At the 

 time of their separation these forms were 

 found in both places. What seems a 

 probable explanation of this more rapid 

 change in the Orient may be briefly 

 stated. The configuration of the Orient 

 is such that animals would have a far 

 greater range east and west than north 

 and south. A great mountain range and 

 a great desert are thrown as barriers 

 across the way of the northward and 

 southward movement. In America there 

 is a continuous gateway to the north and 

 south, but barriers to an eastward or 

 westward movement. With such crea- 

 tures as the birds freedom to move 

 north and south would always lessen 

 competition, while the crowding of one 

 group or race upon another eastward or 

 westward would increase the competi- 

 tion. But Geology tells us that in the 

 Orient such westward invasions have ac- 

 tually occurred, causing the death of the 

 less hardy forms and the modification of 

 all forms of animal life. 



It must not be understood, from what 

 has been said, that all the animals, espe- 

 cially the birds, found in any one country 

 or island, are different from the birds 

 found in all others, for that is not true. 

 There are many species of birds that are 

 found practically all over the earth. But 

 what is true is that each country or re- 

 gion of any considerable extent, or group 

 of oceanic islands has some species which 

 are not found anywhere else in the world. 



From what has already been said it 

 will be clear that the world may be divid- 

 ed into several different regions, accord- 

 ing 10 the animals which are peculiar to 

 the different ones. Following Newton's 

 system, because it seems the most logi- 



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