The Evolution-idea is a master-key that opens many doors. It is a luminous interpretation of the world, throwing the light of the past upon the present. Everything is seen to be an antiquity, with a history behind it - a natural history, which enables us to understand in some measure how it has come to be as it is. We cannot say more than "understand in some measure," for while the fact of evolution is certain, we are only beginning to discern the factors that have been at work.
This excerpt was published almost 70 years ago, well before the molecule of heredity was explained, before modern genetics, before molecular biology and proteomics, and still affirms the fact of evolution, which slightly took me by surprise. The exact mechnism of natural selection was unknown at this point in history, but evolution was still undeniably true in this textbook, which I am sure, was not an assertion reflected by the general public.
I suppose what amazes me is that we are largely in the same place in history; evolution is still touted as just a theory and is sequestered (along with natural history in general) into the "special interest" category. I would go so far to say that the scientific community in general is looked upon as special interest group in America.
So the evolution of the acceptance of evolution has never changed in the scientific community. Once Mendelian genetics was incorporated into Darwin's theory, natural selection was rejuvinated, quickly becoming cornerstone of biology.