THE FACTORS OF ORGANIC EVOLUTION. [rr 
modification takes place. I believe it is safe to say that 
a majority of the cases which are supposed to prove the 
inheritance of acquired characters prove only that char- 
acters are acquired, not that they are 
: inherited. There is great need of cau- 
ea tion against supposing that any charac- 
proteplaem'? ter is inherited unless it repeats itself 
under many and different conditions. 
Apart altogether from inheritance, similar conditions 
may produce similar results, and consequently this 
source of error must be eliminated if we would be cer- 
tain that the structure of the germinal protoplasm has 
really been modified. Many of the alleged cases of the 
inheritance of mutilations, of the direct influence of the 
environment, and of use and disuse, fall away under this 
precaution. 
The general evidence for the inheritance of mutila- 
tions is so notoriously bad that I pass it by altogether 
and select for consideration a few cases, chosen from a 
recent work on the subject,* which have by various 
writers been alleged as showing the direct influence of 
environment in modifying species and also the inherited 
effects of use and disuse. 
(2) It is well known that certain gasteropods if 
reared in small vessels are smaller than when grown in 
large ones, and this case has been cited 
as showing the influence of environment 
in modifying species. There is good 
evidence, however, that this modification does not affect 
the germinal protoplasm, for these same gasteropods 
will grow larger if placed in larger vessels. It seems 
very probable that the diminished size of these animals 
is due to deficient food supply, but this has so little 
Do external 
Diminished 
nutrition. 
*E, D. Cope. The Primary Factors of Organic Evolution, 
1896. 
9 
