Note F — PREFATORY NOTE.

Nägeli, like Weismann, arrives at the conclusion that acquired characters are not inherited. He was not content, however, to rest the generalization upon purely speculative grounds, but undertook the experimental demonstration. After seventeen years of work by himself and son, especially upon several species of Hieracium, he satisfied himself that his theory was true to the facts. We all know now how far he fell short of settling the question.—Trans.