INTRODUCTION. ]xi 



to producL' strains noticeable for this or that peculiarity useful to tlieir owners. Dar- 

 win apjilied this law to animals and plants existing in a state of nature, i. e., wild or 

 uncultivated ; and claimed that a process of natural selection is going on throughout 

 the world. This phase of evolution is called 'Darwinism.' The work entitled The 

 Origin of Species, comprising the results of thirty years of observation and reflec- 

 tion, was published to support and confirm this special theory. 



We will give a condensed statement of the theory of natural selection, from the 

 author's own recapitulation of his views, presented at the end of his work (fifth 

 edition, 1871), often using his own words. Domestic animals vary greatly, as the 

 result of changed conditions of life. " This variability is governed by many complex 

 laws — by correlation, by use and disuse, and by the definite action of the surround- 

 ing conditions." " Man does not actually produce variability; he only unintentionally 

 exposes organic beings to new conditions of life, and then nature acts on the organi- 

 zation and causes vari.ability." "There is no obvious reason why the principles which 

 have acted so efliciently under domestication should not act under Nature. In the 

 survival of favored individuals and races, during the constantly recurring struggle for 

 existence, we see a powerful and ever-acting form of selection. . . . More individuals 

 are born than can possibly survive. ... As the individuals of the same species come 

 in all respects into the closest competition with each other, the struggle will generally 

 be most severe between tliem ; it will be almost equally severe between the varieties 

 of the same species, and next in severity between the species of the same genus. On 

 the other hand, the struggle will often be very severe between beings remote in the 

 scale of nature." 



"With animals having separated sexes, there will be in most cases a struggle 

 between the males for the possession of the females. The most vigorous males, or 

 those which have most successfully struggled with their conditions of life, will gener- 

 ally leave most progeny. But success will often depend on the males having special 

 weapons or means of defence, or charms ; and a slight advantage will lead to victory." 



He then claims that, as geology shows that each land has undergone great physical 

 changes, we might have expected to find that organic beings have varied under Nature 

 in the same way as they have varied under domestication. " If, then," he says, "ani- 

 mals and plants do vary, let it be ever so little or so slowly, why should we doubt that 

 the variations or individual differences, which are in any way beneficial, would be 

 preserved and accumulated through natural selection, or the survival of the fittest? If 

 man can by patience select variations useful to him, why, under changing and complex 

 conditions of life, should not variations useful to Nature's living products often arise, 

 and be preserved cr selected." 



It is impossible, without the evolution theory, to explain the meaning of rudimen- 

 tary organs. " Disuse, aided sometimes by natural selection, has often reduced organs, 

 when they have become useless under changed habits or conditions of life ; and we 

 can clearly understand on this view the meaning of rudimentary organs. But disuse 

 and selection will generally act on each creature when it has come to maturity, and 

 has to play its full part in the struggle for existence, and will thus have little power 

 on an organ during early life: hence the organ will not be reduced or rendered rudi- 

 mentary at this early age. The calf, for instance, has inherited teeth which never cut 

 through the gums of the upper jaw from an early progenitor having well-developed 

 teeth ; and we may believe that the teeth in the mature animal were reduced, during 

 successive generations, by disuse, or by the tongue and palate or lips having become 



