282 Heredity. 



cated organ will thus, if the yarious modifications are 

 really fortuitous, require a very great number of genera- 

 tions to supply the necessary variations. 



There does not seem to be any logical ground for 

 doubting that any of the adaptations of nature might 

 have been produced by the natural selection, from an in- 

 definite number of fortuitous variations, of those which 

 happened to be favorable; but in the case of any com- 

 plex adaptation, an indefinite and almost infinite period 

 of time would be required. 



Darwin says {Origin of Species, p. 143) that reason 

 tells us that if numerous gradations from a simple and 

 imperfect eye to one complex and perfect can be shoAvn 

 to exist, each grade being useful to its possessor, as is 

 certainly the case; if further the eye ever varies, and 

 these variations be inherited, as is likewise certainly the 

 case; and if such variations should be nseful to any ani- 

 mal under changed conditions of life, then the difficulty 

 of believing that a perfect and complex eye could le 

 formed by natural selection, though insuperable by our 

 imagination, should not be considered as subversive of 

 the theory. Before we can accept as possible this view 

 of the evolution of the eye '' we must suppose each new 

 state of the instrument to be multiplied by the million; 

 each lo be preserved until a better one is i:)roduced, and 

 then the old ones to be all destroyed. . . . Let this 

 process go on for millions of years; and during each year 

 on millions of individuals of many kinds; and may we 

 not believe that a living optical instrument might thus 

 be formed as superior to one of glass as the works of the 

 Creator are to those of man?" 



To show that complex adaptatio*ns might have leen 

 produced by the selection of fortuitous variations is by 

 no means to prove that they have thus been produced, 

 and we may well doubt whether life has existed long 



