PRESIDENTIAL ADDRESS. 63 



in the development of plant life and have from time to time 

 within the past fifteen j-ears presented this theme from every 

 point of view that I have been able to see it. I recognize the 

 law of natural selection as probabh^ the most potent of all or- 

 ganic laws, but I have never doubted that a great part of the 

 variations upon which its action depends are due to reactions 

 of the organism upon the environment, and after reading Weis- 

 mann's essays and ever}- scrap of discussion that I ha\e been 

 able to find arising from them, I am still so dull as to remain 

 unconvinced that such modifications are incapable of hered- 

 itar}' transmission. To sa}- that the environment may and 

 must influence the germ, but that it can onh* influence it in 

 a hap-hazard wa}- analogous to that in which a jar aflects 

 the figures of a kaleidoscope, is to my mind a begging of the 

 question, and I prefer to assume that there is a causal con- 

 nection between the nature of the influence on the germ and 

 the alterations that result, especially as the latter are admit- 

 ted to be in harmony with the former. 



If I have succeeded in showing in one of my papers before 

 this Society* that considerable variation is constantl}- taking 

 place irrespective of any advantage to the species, this much 

 at least has been withdrawn from the domain of natural 

 selection, and if these changes are not produced b}- that law 

 there seems no escape from the conclusion that they are caused 

 by some unknown external influences. 



In the foregoing review of the work that has been done 

 toward the scientific demonstration of the transmissibility of 

 functionally acquired characters I do not pretend to have 

 given the arguments themselves. I have onl}- pointed out the 

 fact that they have been presented, by whom, from what 



* Fortuitous Variation as illustrated b}' the genus Eupatorium. Ab- 

 stract in Nature (London) Vol. XLI, July 25, 18S9, p. 310. 



