318 CONCLUDING CHAPTER 
Now we saw that there seems to be good evidence 
that normal or continuous variations are inherited. 
Logic does not, however, permit us to make the step: 
Acquired variations are continuous variations; con- 
tinuous variations are inherited; therefore acquired 
variations are inherited. It seems, indeed, to be this 
fallacy which has led to the long-continued belief in 
the inheritance of acquired characters as an important 
factor in organic evolution, in spite of so many argu- 
ments to the contrary. 
Formal disproof of this proposition is very difficult, 
and in the meantime the confusion between continuous 
acquired variations and continuous genetic variations, 
which is always present in practice, constitutes a very 
serious drawback to the biometric method of research. 
At present Johannsen’s explanation of these phenomena 
seems to afford so much the simplest solution that 
we may once more repeat his statement of the case, 
though with the proviso that the proof of his hypothesis 
is still to be awaited. 
Johannsen looks upon a population which, as a 
whole, exhibits continuous or normal variability, as 
being capable of analysis into a number of pure lines. 
In a single pure line genetic variability is sensibly 
absent. The members of such a pure line exhibit, 
however, very considerable acquired variability, so 
that in this way each line shows a normal variability 
of its own. And the range of this variability may 
greatly exceed the limits which separate two pure lines 
from one another. The result is to give a completely 
blurred picture when all the lines are looked at simul- 
taneously. And thus the normal variability of the 
