292 OBITUARY x 
Considering the difficulties which surround the 
question of the causes of variation, it is not to be 
wondered at, that Darwin should have inclined, 
sometimes, rather more to one and, sometimes, 
rather more to another of the possible alternatives. 
There is little difference between the last edition 
of the “ Origin ” (1872) and the first on this head, 
In 1876, however, he writes to Moritz Wagner, 
“Tn my opinion, the greatest error which I have 
committed has been not allowing sufficient weight 
to the direct action of the environments, 7.¢., food, 
climate, &c., independently of natural selection. 
. When I wrote the ‘ Origin,’ and for some 
years afterwards, I could find little good evidence 
of the direct action of the environment ; now there 
is a large body of evidence, and your case of the 
Saturnia is one of the most remarkable of which 
I have heard.” (III, p. 159.) But there is really 
nothing to prevent the most tenacious adherent e 7 
the theory of natural selection from taking any | 
view he pleases as to the importance of the direct — 
influence of conditions and the hereditary trans- 
missibility of the modifications which they produce, 
Tn fact, there is a good deal to be said for the view — 
that the so-called direct influence of conditions is 
itself a case of selection. Whether the hypothesis — 
of Pangenesis be accepted or rejected, it can hardly ~ 
be doubted that the struggle for existence goes on — 
not merely between distinct organisms, but between — 
the physiological units of which each organism is — 
