254 ANIMAL SKETCHES. CHAP. 



finest pieces of comb, built with every advantage for 

 securing regularity, show that, so far from every cell being 

 geometrically accurate, it is difficult to find a hexagon 

 presenting errors of less than three or four degrees in its 

 angles. And Mr. Cowan in his admirable little volume on 

 The Honey Bee gives illustrations which bring the irregu- 

 larity home to the eye. In place of the notion that the 

 hexagonal cell-structure is due to a geometrical instinct, 

 there is nowadays a growing tendency to accept a modifi- 

 cation of Buffon's explanation of the origin of cell-structure. 

 Buffon attributed the regularity of the cells to mutual 

 pressure ; in illustration whereof he packed a closed vessel 

 with dried peas, and filled up the interstices with water. 

 The peas, which were thus caused to swell, assumed, under 

 the pressure which resulted, the form of more or less 

 accurate geometrical figures. Perhaps a still better illus- 

 tration of this principle of mutual interaction is seen in 

 soap-bubbles. If a little soapy water be placed in the 

 bottom of a tumbler and air be blown into the water 

 through a tube until the upper part of the glass is full of 

 bubbles, the hexagonal form which these bubbles assume 

 under mutual pressure, and the trilateral pyramids at 

 their bases, will be readily seen. Not that these geome- 

 trical figures are the same as those which the wax assumes, 

 but they illustrate the principle. For, at the temperature 

 of the hive, the wax, pared thin by the smooth-edged jaws 

 of the workers, has all the plasticity of a fluid membrane. 

 The bee has indeed to avoid the danger of paring away too 

 far, and thus making a hole through the wall. But even 

 here she may be aided by mechanical conditions. If we 

 take a thin piece of soap and pare away one face with the 

 blade of a pocket-knife, we shall soon form a transparent 

 patch where the soap is very thin. But if we continue to 

 pare, we do not cut through the soap at this point ; but 



