1 86 Inheritance of Acquired Characters 



"I need not recall," continues our author, "the host 

 of positive changes undergone by plants which cannot 

 be explained by the Lamarckian theory, the appropri- 

 ately placed protective spines, bristles and hairs, the 

 poisons, the tannins, the etherial oils of all kinds, and 

 all the purposeful forms of leaves, of flowers and all 

 parts of plants in general. In the case of all these the 

 supposed inheritance of the effects of use and disuse 

 in general does not come into question; in them every- 

 thing proceeds without it, an incontestable proof that 

 nature does not require this supposed factor for its trans- 

 formations." 148 It is probable on the contrary that 

 many of these changes undergone in the past or in the 

 characters now existing are rather simply the result of 

 the reaction of the plant organs to a certain external 

 or internal stimulus which has not yet been remarked 

 nor indeed suspected. To this category belong very 

 probably, for instance, all the various secretions of 

 chemical substances. Further the very fact that secre- 

 tions that are entirely alike occur in plant species that 

 are quite unlike one another in everything else, speaks, 

 as we shall see at once, in favor of the hypothesis that 

 these same secretions are acquired and inherited char- 

 acters. Other characters which likewise were formerly 

 in all probability functional adaptations or are such now 

 can incidentally serve other purposes and can therefore 

 be useful to the species in other ways also, as we stated. 



It is evident that Weismann, in order to support his 

 assertion that natural selection is quite capable of ex- 

 plaining by itself the transformation of species, has 

 allowed himself to be misled into denying arbitrarily 



148 Weismann : Neue Gedanken zur Vererbungsfrage. P. 66. 



