58 Experimental Zoology 
that no experimental proof of this kind has been furnished, 
because it would seem that it ought not to be difficult to make 
crucial experiments that would settle the question at once. It 
is true that many of the latter-day Lamarckians claim that 
effects of this sort are only very slowly brought about, and that 
we should not expect to observe any results that are meas- 
urable in the course of a few generations. It seems to me that 
by taking this position the Lamarckians distinctly avoid the 
real issue; for it is not evident why such effects, if produced 
at all, should not appear at once in the embryo, since they 
appear at once in the adult. 
It is evident that if the effects of use and disuse were inherited, 
many of the adaptations of organisms to their surroundings 
could be quickly attained; for the parts most used would be 
strengthened in successive generations, those less used would 
soon decrease in proportion to their use, and the complicated 
adjustments of the different parts could be accounted for. The 
habits and instincts of animals would also be made to con- 
form to the needs of the animal. These benefits are so obvious 
that it is small wonder that the theory of the inheritance of ac- 
quired character has always had its adherents. But the plausi- 
bility of a theory is not a scientific proof of its worth, and the 
best evidence, viz. that from experiment, that we have at pres- 
ent, does not show that acquired somatic characters are inherited 
through the germ-cells. Moreover, the advocates of the-theory 
overlook a consideration of prime importance. If the effects of 
mutilations and of diseases are also inherited, the results would 
be highly injurious to animals. Considering how often animals 
are injured, we should expect to find the animal kingdom in a 
most dilapidated condition if the accidental injuries of all their 
ancestors were transmitted to subsequent generations. It is 
unfortunate that many of the best-authenticated cases of the 
inheritance of acquired character are those relating to disease. 
In recent years two elaborations of the principle of inheri- 
tance of acquired characters have appeared. Semon has worked 
out Hering’s original suggestion that heredity is racial mem- 
