EFFECTS OF ENVIRONMENT 163 



An enormously greater number of individuals of every 

 kind of animal and plant is produced than can possibly 

 survive. This holds true of the most slowly breeding 

 animals, and is one of the main factors in the Darwin- 

 Wallace theory of evolution. It is evident that those 

 individuals will survive which are best adapted to their 

 environment, and that whatever the other factors in evolu- 

 tion may have been, the obvious fact remains that organisms 

 are adapted more or less perfectly to their environment. 

 Now, if the acquired characters of the parent were trans- 

 mitted to the offspring, all the acquirements good and bad 

 would seem to have an equal chance, and therefore races 

 in a very bad environment must degenerate, those in a 

 very good environment improve. A bad environment must 

 necessarily injure even those individuals that survive. The 

 chief acquirements of the individuals will therefore be to- 

 wards degeneration, not towards improvement. The indi- 

 viduals of each fresh generation would inherit all the 

 injuries the environment caused in their parents, and 

 would in their turn suffer fresh injuries and transmit 

 them to their offspring. Under such conditions a race must 

 be rapidly exterminated. The opposite would happen in 

 the case of a race in a favourable environment. 



No one disputes either the existence or the transmission 

 of inborn variations. This being admitted, natural selection 

 that is, the influence of the environment must have 

 tended always, for so long as variation has occurred and 

 been transmitted, to preserve those organisms which possess 

 variations adapting them more closely to their environment, 

 and to eliminate those that varied in the other direction. 

 The more stringent the selection, particularly in the way of 

 disease, the more injurious the transmission of acquired 

 characters must be to the race. But variation occurs in 

 every direction, and it is more than probable that the 

 germplasm may sometimes vary towards being influenced 

 by the action of the environment upon the parents. If it 

 varies thus, the effect upon the race must be injurious. 



