Science, spirit, superstition / Constantin Brunner: p. 507.

Not a grain of truth is contained in the assertions regarding mutation and heredity, i.e. the heredity of acquired characteristics, as advanced by the theory of evolution. Essentially we know of only two instances of hereditary transmission of acquired characteristics: those acquired by alcoholism and syphilis. But here we actually can speak only of a passing on of a corruption of the organism and not of the emergence of a new hallmark of the species in the sense of the theory of evolution. Mendel, who is beginning to live only now after his death, has given us the real scientific theory of heredity without mutation. Not, of course, the explanation, but the knowledge of heredity. With this knowledge we now possess the final empirical refutation of the entire evolutionary-metaphysical incubus; and more soundly based than ever now appears the truth of the constancy of species. There is no natural mutation, and we are not capable of producing it artificially except within those limits which the potentialities of the species permit. The species, therefore, remains immutable within the sphere particular to itself inclusive of all possible variations under all possible conditions, and can never put forth a new species from within itself-such, in brief, is the impregnable result of Mendelism. Whatever difficulties still remain are inherent in the uncertainty which, understandably, still attaches to our systematic classification of species. Mendel's feat for biology has been evolution's executioner.