The Decisive Experiment 171 
ence of the limb or other part of the body which was 
destroyed in the parent. 
In order to make this more apparent let us con- 
sider some one of the numerous rats from which 
Weismann cut off the tails, and which that author has 
rightly brought forward as proving that the surgical 
operation of amputation is not inherited. Let us sup- 
pose that in the young rat when once his development 
was completed and he had arrived at about the age at 
which the old rat had undergone the amputation, really 
showed at the spot at which the amputation took place 
a tendency to reproduce the same phenomena of cicatri- 
zation and reestablishment of the new local equilibrium 
which had supervened in the parent. It is evident that 
the absence of the tail is a necessary condition in order 
to make the reproduction of these phenomena materially 
possible. This tendency must then be hindered and per- 
haps absolutely suppressed so long as the tail remains a 
part of the organism. 
It is interesting in this connection to note that Kohl- 
wey has obtained in one and the same individual a com- 
pletely negative result in respect to the inheritance of 
mutilations, but a positive result in respect to the trans- 
mission of habit: He cut off the posterior digit from 
the feet of some pigeons which thereupon turned back 
another digit in order to retain their perch; and in one 
instance this habit was reproduced.'** 
The decisive experiment upon the inheritance of ac-. 
quired characters must leave amputations and similar 
sudden variations out of consideration, since either their 
effect is to bring about the reestablishment of an exclu- 
18017 Kohlwey: Arten und Rassenbildung. Eine Einfithrung in 
das Gebiet der Tierzucht. Leipzig, Engelmann, 1897, P. 6—7. 
