CONTENTS xv 



" Natural Selection tends only to make each organic being as per- 

 fect as, or slightly more perfect than, the other inhabitants of 

 the same country with which it comes into competition." " It 

 will not produce absolute perfection." 



•' Natural Selection cannot possibly produce any modification in a 

 species exclusively for the good of another species." 



Missing Links. Erroneous ideas as to the true nature of " links," 

 and as to their supposed absence. " Links " are nearly always 

 indirect, rarely direct ; they may combine the special charac- 

 ters of both the forms they connect, but more usually have the 

 characters of neither. The true link between an}- two forms is 

 afforded by the common ancestor from whom both alike are 

 descended. Examples of links of various kinds. 



Persistent Types. Many instances are known of genera of animals 

 which have persisted, without appreciable modifications in 

 structure, for enormously long periods, and in some cases from 

 Silurian times to the present day. The occurrence of such 

 persistent types is in no way opposed to the Theory of Natural 

 Selection 



Degeneration or Retrograde Development. An animal may be less 

 highly organised when adult than it is in its earlier stages of 

 existence. During development, organs such as eyes, legs, etc., 

 that are present in the young animals may disappear or become 

 vestigial. This again is not opposed to the theory of Natural 

 Selection. Natural Selection tends to preserve those forms 

 which are best adapted to their environment, and not necessarily 

 those which are ideally most perfect. Examples of degeneration 

 of individual organs, and of entire animals. 



Difficulty as to the persistence of lowly organised animals alongside the 

 higher forms. 



Alleged uselessness of small variations. The whole theory and practice 

 of breeding domestic animals depend on selecting the right 

 animals by scrupulous attention to minute differences. The 

 objection that the right variation may not be present is met by 

 the fact that variation affects all organs and occurs in all 

 directions. 



Difficulty as to the earliest commencement of organs. Natural Selection 

 can only act on an organ after it has already attained sufficient 

 size to be of practical importance and utility. The Theory of 

 Change of Function : an organ may lose its original purpose and 

 yet persist because it is of use for some other purpose : one of 

 these purposes may predominate at one time, another at 



