INSTINCT 209 



completed cells. It suffices that the bees should be 

 enabled to stand at their proper relative distances from 

 each other and from the walls of the last completed 

 cells, and then, by striking imaginary spheres, they 

 can build up a wall intermediate between two adjoin- 

 ing spheres ; but, as far as I have seen, they never 

 gnaw away and finish off the angles of a cell till a large 

 part both of that cell and of the adjoining cells has 

 been built. This capacity in bees of laying down under 

 certain circumstances a rough wall in its proper place 

 between two just-commenced cells, is important, as it 

 bears on a fact, which seems at first quite subversive of 

 the foregoing theory ; namely, that the cells on the 

 extreme margin of wasp-combs are sometimes strictly 

 hexagonal ; but I have not space here to enter on this 

 subject. Nor does there seem to me any great diffi- 

 culty in a single insect (as in the case of a queen-wasp) 

 making hexagonal cells, if she work alternately on the 

 inside and outside of two or three cells commenced at 

 the same time, always standing at the proper relative 

 distance from the parts of the cells just begun, sweep- 

 ing spheres or cylinders, and building up intermediate 

 planes. It is even conceivable that an insect might, 

 by fixing on a point at which to commence a cell, and 

 then moving outside, first to one point, and then to 

 five other points, at the proper relative distances from 

 the central point and from each other, strike the 

 planes of intersection, and so make an isolated 

 hexagon : but I am not aware that any such case has 

 been observed ; nor would any good be derived from a 

 single hexagon being built, as in its construction more 

 materials would be required than for a cylinder. 



As natural selection acts only by the accumulation 

 of slight modifications of structure or instinct, each 

 profitable to the individual under its conditions of life, 

 it may reasonably be asked, how a long and graduated 

 succession of modified architectural instincts, all 

 tending towards the present perfect plan of construc- 

 tion, could have profited the progenitors of the hive- 

 bee ? I think the answer is not difficult : it is knowD 



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