The fact that, with a healthy stock of bees, the interior of a hive always preserves its clean condition, is usually a great puzzle to the novice. In the summer, when the bees are passing continually in and out, this is not so vast a matter for wonder. But in winter-time, when the colony is confined to the hive often for weeks together, it is remarkable that neither the combs nor floor of the hive are ever soiled by excreta. This is a difficulty that the sanitary department in the hive has successfully coped with long ago. It must have been one of the earliest problems that presented itself when the honey-bee first evolved the communal habit. The Ancients believed that all the excreta of the hive were deposited by the bees in certain privy-cells, and thence removed at intervals by the scavenging authorities. There is nothing in this notion, absurd as it is, outside the scope of bee-ingenuity; on the contrary, such a crude device would be little likely to commend itself to the hive-people, as it would be ridiculously inadequate to the case. How great must be the problem of the preservation of cleanliness in a hive, can only be understood when the whole conditions are considered together, and that from a human standpoint. Putting the figures unwarrantably low, what measure of success could the greatest genius that ever lived among sanitary scientists ever hope to achieve, if he were given the task of keeping in cleanly condition, perfect ventilation, and even temperature, a building where 10,000 individuals were crowded together storey above storey—a building hermetically sealed throughout except for one small opening at the lowest level, which must serve for all purposes of entrance and exit to its denizens, as well as sole conduit for the removal of the foul air and introduction of the pure? The task would be gigantic enough in the summer-time, when a large proportion of the inhabitants were away at work during a greater part of the day; but in winter, when all were continuously at home for weeks together, what conceivable device, or combination of devices, could prevent the building soon developing into first a quagmire and then a charnel-house, to which the Black Hole of Calcutta would be a model sanitary retreat?