It will perish unaided by its mother, who could not recognise it because she was unable to find the passage she was used to. If we return to-morrow, we shall find it in the gallery, half-broiled by the sun, and already a prey to the flies—once its own prey. Such is the connection in acts of instinct; one leading to the next in an order that the most serious circumstances have no power to alter. After all, what was the Bembex seeking? Her larva, evidently. But to reach this larva she had to enter the burrow, and to enter the burrow she had to find the door, and the mother persists in seeking this door while the gallery lay open with provender and larva all before her. The ruined abode, the endangered family, were for the moment unimportant; all she could think of was the familiar passage reached through loose sand. Let all go—habitation and inhabitant—if this passage be not found! Her actions are like a series of echoes, awaking one another in a fixed order, the following one only sounding when the preceding has sounded. Not because there was any obstacle; the burrow was all open, but for want of the usual entrance the first action could not take place. That decides everything; the first echo is mute, and so all the rest are silent. What a gulf between intelligence and instinct! Through the ruins of the shattered dwelling a mother guided by intelligence rushes straight to her son; guided by instinct she stops obstinately where once was the door. XX MASON BEES Réaumur has dedicated one of his studies to the Chalicodoma of walls, which he calls the Mason Bee. I propose to resume this study, to complete it, and especially to consider it from a point of view entirely neglected by that illustrious observer. And first of all I am tempted to state how I made acquaintance with this Hymenopteron. It was when I first began to teach—towards A.D. 1843. On leaving the Normal School of Vaucluse a few months previously, with my certificate, and the naïve enthusiasm of eighteen, I was sent to Carpentras to manage the primary school belonging to the college. A singular school it was, upon my word, notwithstanding its fine title of “Upper”!—a kind of vast cellar breathing out the damp engendered by a fountain backing on it in the street. Light came in through a door opening outward when the weather allowed of it, and a narrow prison-window, with iron-bars, and little diamond panes set in lead. For seats there was a plank fastened to the walls all round the room; in the middle was a chair guiltless of straw, a blackboard, and a bit of chalk.