AGENCIES, HABITAT, AND GROWTH 95 



youngest and oldest constituents, the differences in en- 

 vironment between the central and peripheral parts, 

 become greater and greater, and the time required to 

 serve the more widely separated constituents becomes 

 longer and longer. 



Hence the longer growth continues, the more the 

 original conditions of growth are altered, and the more 

 the rate of profitable exchange is diminished and the 

 expenditures in exchange increased. Conditions are 

 constantly arising, therefore, where, in order to meet 

 the local difficulties of distribution and exchange, 

 either new kinds of materials must be added, or new 

 methods of growth adopted, or both, if growth is to be 

 maintained. 



Thus, however simple or elemental the method of 

 growth may be in the beginning, or whatever may be 

 the initial character of the growing materials, increase 

 in mass and volume automatically creates development, 

 or the unfolding of new characters. In other words, 

 growth inevitably proceeds from the simple to the com- 

 plex, from the homogeneous to the heterogeneous, be- 

 cause the progress of mere aggregation inevitably 

 creates more complex and heterogeneous conditions 

 for the associated units. Conversely, all methods and 

 stages of development, in their origin, rest on the ulti- 

 mate simplicity of the cosmic germinal stuff. 



All problems of growth and exchange must be 

 solved, as indeed they are, in the order in which they 

 arise, the earlier ones in a more and more precise and 

 certain manner, otherwise there would be no later ones 

 to solve. Hence in every growing body, the growth of 

 new parts, and the formation of an adequate and dur- 



