TRANSMISSION OF MODIFICATIONS 381 



It is true there were deaths during this process, but the 

 selection was insignificant, and the conviction is absolute that 

 the result was in no large sense due to the selective process. 



In the opinion of the writer this is proof absolute of one of 

 three things : 



1. Either the direct transmission of modifications, a thing 

 not difficult to imagine considering the mild sort of transmission 

 involved in reproduction by fission ; 



2. The direct action of the temperature upon the constitu- 

 tion of the protoplasmic basis of life, a contingency not spe- 

 cially applicable in this case, where the germ undergoes but 

 slight development and there is no practical distinction be- 

 tween germ plasm and body plasm ; 



3. Or, if of neither of these, then it is proof of what may 

 be called progressive variation, in which, with a species living 

 under changing conditions, new centers of variability are being 

 constantly established. 



The significant point is that in this instance the deviations 

 are due not to selection but to the direct action of the environ- 

 ment, and we are left to explain cases of this kind by assuming 

 either that the modifications are themselves directly transmitted, 

 or else that the external conditions have influenced the germ as 

 well as the body. 



This is not difficult to believe of such all-pervasive influences 

 as temperature, and it may well be that certain outside influences 

 can make themselves felt in this way when others which, from 

 their nature, may affect the development but cannot reach the 

 germ, will not make themselves permanently felt except through 

 individual adaptation and selection. 



Acclimatization to poisons. That individuals acquire a high 

 resistance to poisons has already been shown. Speaking gener- 

 ally, living protoplasm will soon adjust itself to any chemical 

 influence not fatal or so extremely injurious as to overcome its 

 powers of adaptability. Physicians change remedies frequently 

 for the reason that they soon lose their characteristic action. 



The acquired resistance of man to arsenic and other poisons, 

 of mice to ricin, of the horse to the filtrate of the diphtheria 

 bacillus, of the rabbit to that of hydrophobia, and of animals 



