making their combs. F. Huber tried to mislead their instinct, or rather to put to the proof their reason and cleverness in every possible way, but they always emerged triumphant from the ordeal. For instance, he put bees in a hive the floor and roof of which were made of glass, that is of a body which the bees use very unwillingly for the attachment of their combs, on account of its smoothness. Thus the possibility of building as usual from above downwards, and also from below upwards, was taken away from them; they had no point of support save the perpendicular walls of their dwelling. They thereupon built on one of these walls a regular stratum of cells, from which, building sideways, they tried to carry the comb to the opposite side of the hive. To prevent this Huber covered that side also with glass. But what way out of the difficulty was found by the clever insects? Instead of building further in the projected direction, they bent the comb round at the extreme point, and carried it at a right angle towards one of the inner sides of the hive which was not covered with glass, and there fastened it. The form and dimensions of the cells must necessarily have been altered thereby, and the arrangement of their work at the angle must have been quite different from the usual. They made the cells of the convex side so much broader than those of the concave that they had a diameter two or three times as great, and yet they managed to join them properly with the others. They also did not wait to bend the comb until they came to the glass itself, but recognised the difficulty beforehand,[62] which had been interposed by Huber while they were building with a view to overcome the first difficulty. _Special Habits._ _The Mason-Bee._--This insect closes the roof of its larval cell with a kind of mortar, which sets as hard as stone. A little hole, closed only with soft mud, is, however, left in one part of the roof as a door of exit for the matured insect. It is said that when a mason-bee finds an old and deserted nest, it saves itself the trouble of making a new one--utilising the ready-made nest after having well cleaned it. In Algiers the mason-bees have been observed in this way to utilise empty snail-shells. According to Blanchard, some individuals avoid the labour of making their own nests or houses for their young, by possessing themselves of their neighbours' houses either by craft or by force. 'Does the mason-bee act like a machine,' says E. Menault, 'when it directs its work according to circumstances, possesses itself of old nests, cleanses and improves them, and thereby shows that it can fully appreciate the immediate position? Can one believe that no kind of reflection is here necessary?'