The Inherited Effects of Changes 45 
Pictet, as has been shown in the preceding chapter, has also 
obtained direct evidence of the inherited effects of food. It 
should be noticed in this case that the young caterpillar fed on 
the leaves of a new food plant produces changes of a certain 
type in its somatic cells that appear in the butterfly. The 
caterpillars of these butterflies, reared on their natural food 
plant, produce butterflies that also show evidence of the effect 
caused in the preceding generation. It is probable that this influ- 
ence was directly induced in the germ-cells of the first genera- 
tion, so that the effects were not inherited through the soma, but 
were directly produced. The point, however, of special interest 
in these cases, aside from the question of inheritance, is that the 
influences that induce certain changes in the somatic cells of 
the caterpillar affect the germ-cells of that caterpillar in the 
same way, so that when they develop they, too, give the same 
results. The effect is weakened, it is true, in the second genera- 
tion; but this may be due to the counteracting influence of the 
normal food. The results show that the influence of the envi- 
ronment may persist for one or more generations in another 
environment. 
Recently de Vries has dealt with the same subject, and has 
carried out certain experiments that bear on the question. He 
believes that in general the effect of the environment produces 
only the fluctuating variations seen in plants. The full effects 
may not appear at once, but may be accumulated, through sev- 
eral generations, and hence would seem to be inherited. He 
speaks of these changes as acquired characters, and believes, 
as I have said, that individual variations are simply acquired 
characters due to differences in the environment. We are to 
understand, however, that de Vries means that these characters 
are acquired either by the somatic cells or by the germ-cells, 
but independently of each other, z.e. the effects acquired by the 
somatic cells are not supposed to affect the germ-cells except 
indirectly, namely, by affecting the nourishment of the germ- 
cells. 
The question arises whether these new characters are inherited 
