The Development Theory. 205 



But let us now go back a little in our geo- 

 logical history of the continent. It will be 

 remembered that the development of our con- 

 tinent was described as progressive elevations 

 of new portions of sea bed, like so many added 

 fields to an old farm. 



If now r we add the statement that each of 

 these annexed fields was in its turn stocked 

 with plants and animals suitable to its period, 

 we have the opening of the other half of our 

 subject, development as applied to plants and 

 animals. 



It will be remembered that there were des- 

 ignated ten or more of these annexed fields 

 during the whole period of geological history. 

 All through this history running through mil- 

 lions of years there were, side by side, two 

 kingdoms of life; that of the plant, the vege- 

 table kingdom, that of the animal, the animal 

 kingdom. During all this time the inter-rela- 

 tions of field and flora and of field and fauna 

 were such that each province of each kingdom 

 fits where it is and would fit nowhere else. 

 This triple relationship suggests a wider sys- 



