186 Inheritance of Acquired Characters 
“IT 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 
“®Weismann: Neue Gedanken zur Vererbungsfrage. P. 66. 
