THE 
AMERICAN NATURALIST 
THE PAL/EONTOLOGICAL EVIDENCE FOR THE 
TRANSMISSION OF ACQUIRED CHARACTERS/ 
A S a contribution to the present discussion upon the inherit- 
ance of acquired characters I offer an outline of the opinions 
prevailing among American naturalists of the so-called Neo- 
Lamarckian school, and especially desire to direct attention to 
the character of the evidence for these opinions. This evidence 
is of a different order from that discussed in Weissmann's Essays 
upon Heredity, and while it cannot be said to conclusively 
demonstrate the truth of the Lamarckian principle, it certainly 
admits of no other interpretation at present, and lends the sup- 
port of direct observation to some of the weightiest theoretical 
difficulties in the pure selection principle. 
I. I regard natural selection as a universal principle, ex- 
plaining the " survival of the fittest " individuals and natural 
groups, and as the only explanation that can be offered of the 
origin of one class of useful and adaptive characters. I sup- 
plement this by the Lamarckian principle as explaining the 
" origin of the fittest " in so far as fitness includes those race 
variations which correspond to the modifications in the individual 
springing from internal reactions to the influences of environment. 
