DARWIN AND NATURAL SELECTION 53 



destroy structures produced by them, according to 

 whether those structures are useful or harmful. 



Darwin foresaw the objections which could be 

 raised against his theory, some of which were formu- 

 lated during his life. One of the cases which are 

 most difficult to explain through natural selection is 

 the appearance of organs of extreme perfection and 

 complexity, consisting of numerous parts and unable 

 to function properly unless all their parts are very 

 accurately fitted to one another. Such is for instance " 

 the eye of the higher animals. 



Without solving this difficult problem, Darwin 

 makes the general statement that, as vestigial 

 organs of vision are found in certain animals (and 

 numerous transitional forms can be shown to exist), 

 it should not be hard to believe that a perfect and 

 complex eye could be produced by a series of varia- 

 tions (in fact, variations of the eye have been ob- 

 served), every one of which would prove useful to 

 the species. It cannot be demonstrated that any 

 complex organ exists which could not possibly have 

 resulted from numerous, successive, slight modifica- 

 tions. The transitional grades may have become ex- 

 tinct but it would be erroneous to conclude that they 

 never existed. 



Another objection is that certain organs are too 

 unimportant or too useless to have been preserved 

 by natural selection. What purpose can the giraffe's 



