intervals between these grains can receive, and set the water boiling, all these cylinders will become six-sided columns." Buffon's comparison has been a good deal laughed at, yet it is not altogether bad. He understood that each cell with its sides cut at regular angles was not an individual work, nor the direct execution of the original plan; that it was a kind of resultant brought about by the forced neighborhood, the mutual crowding and hindering of constructions conceived on a simpler plan, and one more usual among insects, the cylindrical chamber.
The humble-bees, which are hymenopterous insects, like honey-bees, put their store of honey away in their old cocoons. When the vessel is too small, they add to it at the opening a prolongation of wax. It may even occur that they build single cells, of an irregular globular form; this is a first step, the primitive wax-working. There is nothing very remarkable yet in this; but the next step becomes more important. Between this rude simplicity and the work, so finished, of the bee, we find something intermediate, the honey-cells of the domestic mélipone, of Mexico. The insect itself forms a transition, by its external marks, between the honey-bee and the humble-bee, and is nearer to the latter. To preserve its honey, it builds a pile of large spherical cells, all placed at equal distances apart, only that this distance is everywhere less than twice the radius of the spheres, so that they all encroach on each other, and are kept apart by a perfectly flat partition, having exactly the same thickness as the curved wall that bounds the free and spherical portion of each cell. If three are found to adjoin, the lines of separation cross at equal angles, and their common meeting-point rests on the top of a pyramid with three walls formed by the three cells, exactly as in a honeycomb. Reflecting on all this, Darwin says the thought occurred to him that, if the mélipone, which already builds its spheres at equal distances apart, were to come to disposing them symmetrically and back to back upon two opposite sides, there would result from this fact a construction as admirable as the bottom of a double rank of cells in the hive.
Has the constructive genius of the wasp and the bee passed through these transitions? It is impossible to assert it; but the evidence shows, and calculation confirms it, that some modifications, slight enough definitely, occurring in the instincts of the mélipone, might lead it, after an indefinite number of ages—we must always calculate on such periods of time—to build those three-angled pyramids which are already found in its constructions, in two or three ranks; then to build upon those pyramids, on each side, prolongations cylindrical in principle, like those which the humble-bee puts on its cocoons, and prism-shaped from their nearness to each other. Besides, such a construction upon a flat surface of its honey-cells by the mélipone would be nothing very extraordinary; in this way it builds the little chambers where it deposits its grubs.