82 THE THEORIES OF EVOLUTION 



death? This question is closely related to another 

 objection to the selection theory. As the variations 

 we mentioned are not very important, the cases in 

 which- they can play such a part must be very few. 

 The famous example of the giraffe's neck has been 

 cited frequently. It was discussed by Darwin him- 

 self and we know his hypothesis according to which 

 a few extra inches in length, enabling an animal to 

 browse on the foliage of higher branches, may become 

 in time of dearth a question of life or death, and more- 

 over a more elongated neck may present other not- 

 able advantages even when that extra elongation is 

 almost insignificant. To this Naegeli answers that 

 the elongation which takes place in the course of one 

 generation is not important enough to constitute a 

 decided advantage and that even if this advantage 

 were real, one could not be assured that all the indi- 

 viduals deprived of it would die in time of dearth ; it 

 is more probable that they would simply become weak- 

 ened. 



This applies to parts of the body showing an in- 

 crease in size. It should apply also to organs which 

 have disappeared. If we attribute their disappear- 

 ance to natural selection alone and not to the inherited 

 effects of disuse, we must demonstrate that their pro- 

 gressive disappearance was useful in every one of its 

 phases. 



The atrophy of the whale's femoral bone is another 



