10 The American Naturalist. [January, 
question do not at all correspond in the child and in the father 
or mother (parent, Weismann), and stand in no genetic con- 
nection. 
Tke arguments which oppose the acceptance of the theory 
of the inheritance of mutilations, have been discussed so much 
in detail, especially by Weisman and Ziegler, that I shall not 
refer further to them here. The objections raised have by no 
means grown weaker of late; they have rather been consider- 
ably strengthened by new investigations which give us a 
deeper insight into the character and processes of fertilization 
(Weismann’s Amphimixis). If now there is no doubt that in 
the acceptance of the transmission of mutilations, and of the 
other peculiarities acquired in the life of the individual, the 
phenomena of the theory of descent find a convenient and 
simple explanation, this condition by no means authorizes 
us to an unconditional acceptance of this supposition, since, 
as Weismann has shown, all phenomena of the theory of de- 
scent may also be explained just as simply and unconstrain- 
edly without the aid of the Lamarckian principle. Of special 
importance for the decision of the question at issue are Weis- 
mann’s much discussed experiments on mice. As is known, 
the artificial mutilations of these animals were carried on in 
both parents through many generations, without any apparent 
success. Similar recently published experiments of Ritzema 
Bos, as well as those of J. Rosenthal, showed also the same 
negative result. If now indeed these experiments on mice, as 
_ Weismann states with especial emphasis, alone and without 
further evidence, by no means furnish direct proof of the 
claim “that injuries cannot at all be transmitted, since such 
experiments must be prosecuted even to infinity : yet, indeed, 
after these unanimously negative results, the possibility of the 
transmission of single mutilations can be put entirely aside, and 
the [inheritance of ?—Trans.] mutilations repeated on both 
parents through many generations, appear at least very improb- 
able. I,as little as Weismann, Ziegler, and others, desire to doubt 
that modifying influence of external interference and stimulus 
on the germ plasm. One can be easily convinced of this, that 
change of climate, altered conditions of temperature, light and 
