THE DIRECT INFLUENCE OF 

 ENVIRONMENT 



BY 

 D. T. MacDOUGAL 



Any serious consideration of the diversity of 

 organisms, of the complexity of the qualities they 

 bear, of the relationships they sustain, and of the 

 character of the stresses under which they exist 

 with relation to the environmental setting, leads 

 inevitably to the conclusion that their evolution- 

 ary development must have been aflPeeted by 

 many modifying agencies; that the origination, 

 or activation of their quahties or characters may 

 not be ascribed to any single causal force or guid- 

 ing factor; and that the course of heredity from 

 generation to generation has been determined 

 by many things beside the simple inertia of prim- 

 itive initial qualities of protoplasm. 



When we join in the accepted generalization 

 that the quahties and forms of organisms now 

 existent are the net result of the action of envi- 

 ronic forces upon ancestral structures, selective 

 as well as initiatory, we implicate a much larger 

 group of conceptions than that embodied in the 

 present thesis, since it is the intention to confine 

 discussion to the possibilities that arise when liv- 



114 



