[2] See, however, the letter from the Times, reprinted on [p. 62].
[3] There is a tendency among writers on Variation, as affording the opportunity for the operation of Natural Selection, to assume that the variations presented by organisms are minute variations in every direction around a central point. Those observers who have done useful work in showing the definite and limited character of organic variations have very generally assumed that they are opposing a commonly held opinion that variation is of this equally distributed character. I cannot find that Mr. Darwin made any such assumption; and it is certain, and must on reflection have been recognized by all naturalists, that the variations by the selection and intensification of which natural selection has produced distinct forms or species, and in the course of time altogether new groups of plants and animals, are strictly limited to definite lines rendered possible, and alone possible, by the constitution of the living matter of the parental organism. We have no reason to suppose that the offspring of a beetle could in the course of any number of generations present variations on which selection could operate so as to eventually produce a mammalian vertebrate; or that, in fact, the general result of the process of selection of favourable variations in the past has not been ab initio limited by the definite and restricted possibilities characteristic of the living substance of the parental organisms of each divergent line or branch of the pedigree.
[5] M. Paul Bourget of the Académie Française, is not only a charming writer of modern ‘novels,’ but claims to be a ‘psychologist,’ a title which perhaps may be conceded to every author who writes of human character. His works are so deservedly esteemed, and his erudition is as a rule, so unassailable, that in selecting him as an example of the frequent misrepresentation, among literary men, of Darwin’s doctrine, I trust that my choice may be regarded as a testimony of my admiration for his art. In his novel Un Divorce, published in 1904, M. Bourget, says: ‘La lutte entre les espèces, cette inflexible loi de l’univers animal, a sa correspondance exacte dans le monde des idées. Certaines mentalités constituent de véritables espèces intellectuelles qui ne peuvent pas durer à côté les unes des autres’ (Edition Plon, p. 317). This inflexible law of the animal universe, the struggle between species, is one which is quite unknown to zoologists. The ‘struggle for existence,’ to which Darwin assigned importance, is not a struggle between different species, but one between closely similar members of the same species. The struggle between species is by no means universal, but in fact very rare. The preying of one species on another is a moderated affair of balance and adjustment which may be described rather as an accommodation than as a struggle.
A more objectionable misinterpretation of the naturalists’ doctrine of the survival of the fittest in the struggle for existence is that made by journalists and literary politicians, who declare, according to their political bias, either that science rightly teaches that the gross quality measured by wealth and strength alone can survive and should therefore alone be cultivated, or that science (and especially Darwinism) has done serious injury to the progress of mankind by authorizing this teaching. Both are wrong, and owe their error to self-satisfied flippancy and traditional ignorance in regard to nature-knowledge and the teaching of Darwin. The ‘fittest’ does not mean the ‘strongest.’ The causes of survival under Natural Selection are very far indeed from being rightly described as mere strength, nor are they baldly similar to the power of accumulating wealth. Frequently in Nature the more obscure and feeble survive in the struggle because of their modesty and suitability to given conditions, whilst the rich are sent empty away and the mighty perish by hunger.
[6] A short discussion of this subject and the introduction of the term ‘educability’ was published in a paper by me entitled ‘The Significance of the Increased Size of the Cerebrum in recent as compared with extinct Mammalia,’ Cinquantenaire de la Société de Biologie, Paris, 1899, pp. 48–51.
It has been pointed out to me by my friend Dr. Andrews, of the Geological Department of the British Museum, that the brain cavity of the elephants was already of relatively large size in the Eocene members of that group, which may be connected with the persistence of these animals through subsequent geological periods.
[7] It would be an error to maintain that the process of Natural Selection is entirely in abeyance in regard to Man. In an interesting book, The Present Evolution of Man, Dr. Archdall Reid has shown that in regard to zymotic diseases, and also in regard to the use of dangerous drugs such as alcohol and opium, there is first of all the acquirement of immunity by powerful races of men through the survival among them of those strains tolerant of the disease or of the drug, and secondly, the introduction of those diseases and drugs by the powerful immune race, in its migrations, to races not previously exposed either to the diseases or the drugs, and a consequent destruction of the invaded race. The survival of the fittest is, in these cases, a survival of the tolerant and eventually of the immune.
[8] ‘Religion means the knowledge of our destiny and of the means of fulfilling it.’—Life and Letters of Mandell Creighton sometime Bishop of London, vol. ii. p. 195.
[9] This has been established in the case of the Trypanosoma Brucei, a minute parasite living in the blood of big game in south-east Africa, amongst which it is disseminated by a blood-sucking fly, the Glossina morsitans or Tsetze fly. The parasite appears to do little or no harm to the native big game, but causes a deadly disease both in the horses and cattle introduced by Europeans and in the more anciently introduced native cattle (of Indian origin). Similar cases are found where a disease germ (such as that of measles) produces but a small degree of sickness and mortality in a population long associated with it, but is deadly to a human community to which it is a new-comer. Thus Europeans have introduced measles with deadly results in the South Sea Islands. A similar kind of difficulty, of which many might be cited, is brought about by man’s importations and exportations of useful plants. He thus brought the Phylloxera to Europe, not realizing before hand that this little parasitic bug, though harmless to the American vine, which puts out new shoots on its roots when the insect injures the old ones, is absolutely deadly to the European vine, which has not acquired the simple but all-important mode of growth by which the American vine is rendered safe. Thus, too, he took the coffee-plant to Ceylon, and found his plantations suddenly devastated by a minute mould, the Himileia vastatrix, which had lived very innocently before that in the Cingalese forests, but was ready to burst into rapacious and destructive activity when the new unadjusted coffee-trees were imported by man and presented in carefully crowded plantations to its unrestrained infection.