STRUCTURE OF CELLS. 79 



sumed. Bees, therefore, in the formation of their 

 cells have to solve a problem in geometry, namely, 

 "a quantity of wax being given, to form of it 

 similar and equal cells of a determinate capacity, 

 but of the largest size in proportion to the quan- 

 tity of matter employed, and disposed in such a 

 juanner as to occupy in the hive the least possible 

 space." Every part of this problem is practically 

 solved by bees. If their cells had been cylindrical, 

 which form seems best adapted to the shape of a 

 bee, they could not have been applied to each 

 other without leaving a number of useless vacant 

 spaces. If the cells had been square or triangular, 

 this last objection would be removed; but a 

 greater quantity of wax would have been required, 

 and the shape would have been inconvenient to a 

 round-bodied animal. Hexagonal cells are admi- 

 rably fitted to the form of the insect, at the same 

 time that their sides apply to each other without 

 the smallest vacant intervals. Another important 

 saving in materials is gained by making a common 

 base serve for two layers of cells. Much more 

 wax as well as room would have been required, 



