INSTINCT 231 



thus made the best cells with least labor, and least waste of honey 

 in the secretion of wax, having succeeded best, and having trans- 

 mitted their 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 in- 

 stincts, that "the variations of structure and of instinct must have 

 been simultaneous and accurately adjusted to each other, as a 

 modification in the one without an immediate corresponding 

 change in the other would have been fatal." The force of this ob- 

 jection rests entirely on the assumption that the changes in the in- 

 stincts 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 ker- 

 nel. Now what special difficulty 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 pur- 

 pose as that of the nut-hatch, at the same time that habit, or com- 

 pulsion, or spontaneous variations of taste, led the bird to become 

 more and more of a seed-eater? In this case the beak is supposed 

 to be slowly modified by natural selection, subsequently to, but in 

 accordance with, slowly changing habits or taste; but let the feet 

 of the titmouse vary and grow larger from correlation with the 

 beak, or from any other unknown cause, and it is not improbable 

 that such larger feet would lead the bird to climb more and more 

 until it acquired the remarkable climbing instinct and power of 

 the nut-hatch. In this case a gradual change of structure is sup- 

 posed to lead to changed instinctive habits. To take one more case: 

 few instincts are more remarkable than that which leads the swift 

 of the Eastern Islands to make its nest wholly of inspissated 

 saliva. Some birds build their nests of mud, believed to be 

 moistened with saliva; and one of the swifts of North America 

 makes its nest (as I have seen) of sticks agglutinated with saliva, 

 and even with flakes of this substance. Is it then very improbable 

 that the natural selection of individual swifts, which secreted more 

 and more saliva, should at last produce a species with instincts 

 leading it to neglect other materials and to make its nest exclu- 

 sively of inspissated saliva? And so in other cases. It must, how- 



