172 Inheritance of Acquired Characters 
sively local equilibrium or the repetition in the 
descendants of the phenomena by which the parent 
organism reacted is hindered. This experiment must 
rather be directed toward modifications of the functional 
adaptation, wihch have a very extensive action and whose 
repetition in the descendants is not hindered by anything. 
In order that these experiments on the changes 
dependent upon functional adaptation may constitute an 
incontestable proof for or against the inheritance of 
acquired characters,—which latter are to be understood 
in Weismann’s sense as only somatic and not general 
peculiarities of the entire organism,—they must be 
planned in such a way as to make it certain that the 
change effected by the transforming influence has affected 
only the soma directly, and for still greater certainty it 
ought to act upon only a definite part of the soma 
and not upon the entire soma to the same extent. They 
must also be undertaken on pluricellular organisms in 
which the somatic germ cells are clearly differentiated, 
and there ought to be employed as transforming influ- 
ences only such as certainly exert no direct influence upon 
the reproductive cells.197 
All plants in which the difference between somatic 
and germ cells is not a thorough going and definite one 
will therefore be less suitable for these researches than 
animals, and particularly higher animals, and all such 
investigations both in animals and in plants which em- 
ploy physical or chemical transforming agents exerting 
a general action on the entire organism, on the somatic 
cells as well as on the germ cells, as for example tem- 
7Compare J. De Meyer: L’hérédité des caractéres acquis est- 
elle expérimentalement vérifiable? Archives de Biologie. Tome XXI, 
No. III and IV. Paris, Masson 1905, P. 625, 634—639. 
