DIRECT INFLUENCE OF ENVIRONMENT 115 



ing or self -generating matter transmits its spe- 

 cialized characters from one generation to an- 

 other in the germ-cell, and displays its periodic 

 somatic expansions in ontogeny. 



Within this definite and restricted field, exact- 

 ness and clearness of comprehension of the rela- 

 tions involved will depend directly upon the thor- 

 oughness with which we may be able to connect 

 our conceptions with the physico-chemical proc- 

 esses of organisms. 



The more important external, direct, or phys- 

 ical factors, the influence of which induces adjust- 

 ments and engages the activities of protoplasm, 

 include radiant energy in its various phases, and 

 the chemical structure of the medium, substratum 

 or substances coming into contact with the living 

 matter and included with its intake and output. 

 These agents interlock intimately with the parts 

 of the self -generating protoplasmic machine, fur- 

 nishing building material, energy in various 

 forms, catalysts, and control reactions in a man- 

 ner so intimate that it is impossible to think of 

 living matter free from its environic setting. 



Now if we set about the calibration of the quan- 

 titative relation of any of these factors to living 

 matter, or attempt an estimation of the qualita- 

 tive effect, we will find that, with respect to any 

 given strain of organisms or any individual, the 

 constellation of specific activities, processes or 

 functions, grouped in the plant are adjusted in 

 such manner that they proceed at the most advan- 



