=The racial poisons and decadence.=--Certain apparent, though not real, exceptions exist to the denial of the Lamarckian theory of the transmission of acquired characters. These exceptions are furnished by what I have called the _racial poisons_. Alcohol, for instance, is a substance, certainly poisonous in all but very small doses, if not in them, which is carried by the blood to every part of the body and may and does injure its _racial_ elements. Thus a true racial degeneration may be caused by its means: and the possibility of this is not to be ignored. Other poisons, such as those of certain diseases, act similarly. We must therefore note in passing a biological factor of historical importance, though hitherto entirely unrecognised by historians, and that is disease. Certain of our diseases, and especially consumption or tuberculosis, are at present making history by their extermination of aboriginal races. Minute living creatures, which we call microbes, are introduced into the new and favourable environment constituted by the blood and tissues of human races hitherto unacquainted with them: and the consequences are known to all. But further, it has lately been suggested as highly probable, by Professor Ross and others, that the fall of Greece, that incalculable disaster for mankind, was due to the invasion not of human foes but of the humble living species which are responsible for the disease miscalled malaria. The evidence for this view is by no means slight, and the most recent explanation of an event so abrupt and so disastrous is in all likelihood the correct one. Malaria, like alcohol, produces true racial degeneration, its poisons affecting those _racial elements_ of which the individual body, biologically conceived, is merely the ephemeral host: recalling the great line of Lucretius, “_et quasi cursores, vitaï lampada tradunt_.” To lame the runner is not to injure the torch he bears--acquired characters are not transmitted; but the racial poison makes dim the lamp ere the runner passes it on. =Selection and racial change.=--But, leaving poisons out of the question, races of men and animals _do_ undergo change, progressive and retrogressive, in consequence of the action of another factor than that advanced by Lamarck: and this is the factor of “natural selection” or “survival of the fittest.” If, of any generation, individuals of a certain kind are chosen by the environment for survival and parenthood, the character of the species will change accordingly. If what we call the best are chosen, their goodness will be transmitted in some degree, and the race will advance: if what we call the worst are chosen, their badness will be transmitted in some degree, and the race will degenerate.