BEES AND WASPS ARCHITECTURE. 175 



plate of wax had been thick enough to admit of the oppo- 

 site basins being deepened (and widened) into cells, the 

 mutual intersection of adjacent as well as opposite bottoms 

 would have given rise, as in the first experiment with the 

 thick plate of wax, to the pyramidal bottoms. Experi- 

 ments with the vermilion wax also showed, as Huber had 

 previously stated, that a number of individual bees work 

 by turns at the same cell ; for by covering parts of grow- 

 ing cells with vermilion wax, Mr. Darwin 



Invariably found that the colour was most delicately diffused 

 by the bees as delicately as a painter could have done it with 

 his brush by atoms of the coloured wax having been taken 

 from the spot on which it had been placed, and worked into the 

 growing edges of the cells all round. 



Such, omitting details, is the substance of Mr. Darwin's 

 theory. In summary he concludes, 



The work of construction seems to be a sort of balance 

 struck between many bees, all instinctively standing at the 

 same relative distance from each other, all trying to sweep 

 eqiml spheres, and then building up, or leaving ungnawed, the 

 planes of intersection between these spheres. 



This theory, while serving as a full and simple expla- 

 nation of all the facts, has, as we have seen, been so fully 

 substantiated by observation and experiment, that it de- 

 serves to be regarded as raised to the rank of a completed 

 demonstration. It differs from the theory of Buffon in 

 two important particulars : it embraces all the facts, 

 and supplies, a cause adequate to explain them. This 

 cause is natural selection, which converts the random 

 ' pressure ' in Buffon's theory into a precisely regulated 

 principle. Eandom pressure alone could never produce 

 the beautifully symmetrical form of the hexagonal cell 

 with the pyramidal bottom ; but it could and must have 

 produced the intersection of cylindrical cells among pos- 

 sibly many extinct species of bees, such as the Melipona. 

 Whenever this intersection occurred in crowded nests, it 

 must clearly have been of great benefit in securing 

 economy of precious wax ; for in every case where a flat 

 wall of partition between two adjacent cells did duty 

 9 



