382 THE ORIGIN OF SPECIES 



liaving succeeded best, and having transmitted tlieir 

 newly acquired economical instincts to new swarms, 

 which in their turn will have had the best chance 

 of succeeding in the struggle for existence. 



Objections to the Theory of Natural Selection as applied to 

 Instincts: Neuter and Sterile Insects 



It has been objected to the foregoing view of the 

 origin of instincts that "the variations of structure and 

 of instinct must have been simultaneous and accurately 

 adjusted to each other, as a modification in the one i 

 without an immediate corresponding change in the other I 

 would have been fatal." The force of this objection rests i 

 entirely on the assumption that the changes in the instincts i 

 and structure are abrupt. To take as an illustration the 

 case of the larger titmouse (Parus major) alluded to in a 

 previous chapter; this bird often holds the seeds of the 

 yew between its feet on a branch, and hammers with its 

 beak till it gets at the kernel. Now what special diffi- 

 culty would there be in natural selection preserving all 

 the slight individual variations in the shape of the beak, 

 which were better and better adapted to break open the 

 seeds, until a beak was formed as well constructed for: , 

 this purpose as that of the nuthatch, at the same time \ 

 that habit, or compulsion, or spontaneous variations ofi J 

 taste, led the bird to become more and more of a seed- 

 eater ? 



In this case the beak is supposed to be slowlj 

 modified by natural selection, subsequently to, but iii 

 accordance with, slowly changing habits or taste; but lej 

 the feet of the titmouse vary and grow larger from coFj 

 relation with the beak, or from any other unknown causcj 



