244 EN TOMOLOGY 
less, chiefly for two reasons. First, there is no little disagree- 
ment as to what is meant by the term “ acquired characters.” 
An acquired character arises, not in the germ cells, but in the 
soma, or body, and for the theoretical transmission of the 
character the soma must affect the germ cells subsequently ; 
though some maintain that a given external influence may 
affect both soma and germ plasm at the same time. ‘The defi- 
nition of acquired characters excludes (1) sports; (2) changes 
due to the renewed action of the environment upon successive 
generations’ of an organism; (3) changes which may have 
been due to selection. Second, having defined the term, it is 
often difficult if not impossible to say whether a given charac- 
ter is acquired or not. Thus in an acclimatization experiment, 
if heat, for example, affects first the soma and the latter affects 
the germ cells subsequently, we have an example of the inheri- 
tance of an acquired character. If, however, the heat affects 
soma and germ plasm simultaneously, the result is or is not 
the inheritance of an acquired character, according as one de- 
fines the term. Indeed, Weismann himself has found the 
greatest difficulty in trying to explain the inheritance of “ cli- 
matic” variations in terms of his well-known hypothesis. In 
fact, the distinction between acquired and non-acquired charac- 
ters is to no little extent artificial and arbitrary; and too strong 
an insistence upon the distinction bars the way to the solution 
of the more important question—What kinds of variations are 
inheritable and what are not? 
To summarize: Of somatogenic, or acquired, characters, 
(1) injuries or mutilations are unadaptive and probably unin- 
heritable. (2) Functional variations are adaptive, but the 
subject of their transmissibility is involved in doubt. As yet 
there is no adequate experimental evidence upon the subject, 
the discussion of which, therefore, is based chiefly on theoret- 
ical grounds. There is a strong tendency, however, to believe 
that results of use or disuse are to some extent transmissible 
to the benefit of succeeding generations, and even Weismann, 
the chief opponent of the Neo-Lamarckians, admits that the 
