Now, it is quite true that soaked peas in a bottle will take this shape in swelling, but the analogy will not hold good in respect of comb-building. In the work of the bees there is no pressure or constriction of any kind. Each cell is made separately, being joined on to those above it; and the comb expands steadily downward and sideways through an empty space until the desired limit is reached. A much more probable explanation of the hexagonal form of the cell is that it was arrived at by experience. The first combs may have been built with round cells, the interstices being filled in with wax. But the bee, who is an expert in the science of economy, would quickly see the disadvantage of this plan. And with the hexagonal principle, an old familiar thing in the hive—witness the pattern on the egg-surfaces, and the compound eye-construction—it would not be long before she hit upon the better, more scientific way. There is, however, another reason, and almost as potent a one, for the adoption of the six-sided cell both for brood-raising and the storing of honey. It must be remembered that the present system of vertical walls parallel and close together, made up of numberless small horizontal chambers placed back to back, is not an ideal arrangement either for the raising of the young or the storing of food. Yet it is the best possible contrivance under the circumstances, which are forced upon the bee by the necessity of leading a close, crowded, communal life. Air is a prime need for all operations in the hive, but for none more than the development of the young bees. When a queen is to be raised, a full supply of fresh air is given her, but only at the expense of valuable space. With the common kind, of which perhaps ten or fifteen thousand may be maturing in the brood-nest at one and the same time, it is obviously impossible to make any such concession. The young worker- or drone-larva must secure what air it can through the narrow cell-top. Now, the bee breathes at all stages of its career not through the mouth, but by means of air-holes or spiracles in the sides of its body. If the cell were round, the larva, when fairly grown, would fill the space, and the air would reach the spiracles only with difficulty. But, no matter what the size of the young grub may be, the angles of the hexagon cell are never quite filled. They form half a dozen by-passes for the air, arranged on all sides, and extending right to the base of the cell; and thus the larva has the full benefit of the available air-supply, even though it be necessarily scanty.