OF ENVIRONMENT 117 



to the progeny, both in functional capacity and 

 accompanying structure. 



ADJUSTMENT OF THE INDIVIDUAL TO ALTER- 

 ING ENVIRONMENTS 



Let us take, for example, a plant standing in 

 the open in a habitat in which it is firmly estab- 

 lished, and introduce some modifications of wide 

 range of the insolation, which may or may not 

 register with anything previously encountered by 

 this individual. The primary or direct effect of j 

 the change will undoubtedly be a modification of [ 

 the reaction- velocities of some of the chemical' 

 processes so that metabolism and all of the hfe- 

 phenomena dependent upon it will undergo alter- 

 ations in rate, cell-division, chromosomatic invo- 

 lution, catalyptic action involving respiration, 

 intake and excretion, and finally growth also. 

 A secondary effect accompanying these changes 

 will be due to the irritabihty of the living matter 

 by which sudden changes in almost any external | 

 factor will exercise a releasing or unloosing ac- 

 tion.'- Outward manifestations of such action are 

 seen in the various thermotropic and heliotropic 

 movement of leaves, and while there seems to be 

 a disposition on the part of some physiologists to 

 eliminate metabolic activities from the realm of 

 irritable reactions, yet it does not seem justifiable 

 upon present evidence. 



Whether an irritational phase intervenes or 

 aaot, when an environmental factor undergoes 



