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- 

 ronmeiit 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 

 beheves 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, i.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 



