370 
If we refer to “Weismannism up to date,” as Mr. Romanes 
so happily indicates the latest teaching of this great 
savant, we shall find that he has arrived now at a definite 
conclusion. 
“ Many climatic varieties of plants may also be due wholly or in 
part to the simultaneous variation of corresponding determinants 
in some part of the soma and in the germ plasm of the repro 
ductive cells, and these variations must necessarily be hereditary.” 
—(The Germ Plasm, ft. 406.) 
Speaking of amphimixis, he says :— 
“ It is not the primary cause of hereditary variation. By its means 
those specific variations which already exist in a species may con 
tinually be blended in a fresh manner, but it is incapable of giving 
rise to new variations even though it often appears to do so. . . . 
The cause of hereditary variation must lie deeper than this. It must 
be due to the direct effect of external influences on the biophors 
and determinants.”—(The Germ Plasm, ftft. 414-13.) 
Now the effect of this modification of the theory is 
enormous ; for whereas the denial of any change of the 
continuous germ plasm, due to the effect of changed 
conditions, emphasised the importance of sexual repro 
duction as the sole means of modification, and variations 
thus produced could only be fixed in a race living 
in a state of nature by the principle of Natural Selec 
tion, the admission that external influences produce 
a direct effect upon the germ plasm and are the sole 
source of new variations establishes the influence of the 
principle of the action of external conditions, so as to 
render Natural Selection no longer necessary. The effect 
of all this is to make the theory of the continuity of the 
germ plasm the ally of Lamarckism rather than of 
Darwinism. 
And this result is not affected by some of the modifi 
cations of the theory. The essential point is that the