Now that the facts are set forth, let us, if possible, trace the cause. In a horizontal tube, gravity no longer acts to determine the direction which the insect will take. Is it to attack the partition on the right or that on the left? How shall it decide? The more I look into the matter, the more do my suspicions fall upon the atmospheric influence which is felt through the two open ends. Of what does this influence consist? Is it an effect of pressure, of hygrometry, of electrical conditions, of properties that escape our coarser physical attunement? He were a bold man who should undertake to decide. Are not we ourselves, when the weather is about to alter, subject to subtle impressions, to sensations which we are unable to explain? And yet this vague sensitiveness to atmospheric changes would not be of much help to us in circumstances similar to those of my anchorites. Imagine ourselves in the darkness and the silence of a prison-cell, preceded and followed by other similar cells. We possess implements wherewith to pierce the walls; but where are we to strike to reach the final outlet and to reach it with the least delay? Atmospheric influence would certainly never guide us. And yet it guides the insect. Feeble though it be, through the multiplicity of partitions, it is exercised on one side more than on the other, because the obstacles are fewer; and the insect, sensible to the difference between those two uncertainties, unhesitatingly attacks the partition which is nearer to the open air. Thus is decided the division of the column into two converse sections, which accomplish the total liberation with the least aggregate of work. In short, the Osmia and her rivals 'feel' the free space. This is yet one more sensory faculty which evolution might well have left us, for our greater advantage. As it has not done so, are we then really, as many contend, the highest expression of the progress accomplished, throughout the ages, by the first atom of glair expanded into a cell? CHAPTER 2. THE OSMIAE. February has its sunny days, heralding spring, to which rude winter will reluctantly yield place. In snug corners, among the rocks, the great spurge of our district, the characias of the Greeks, the jusclo of the Provencals, begins to lift its drooping inflorescence and discreetly opens a few sombre flowers. Here the first Midges of the year will come to slake their thirst. By the time that the tip of the stalks reaches the perpendicular, the worst of the cold weather will be over. Another eager one, the almond-tree, risking the loss of its fruit, hastens to echo these preludes to the festival of the sun, preludes which are too often treacherous. A few days of soft skies and it becomes a glorious dome of white flowers, each twinkling with a roseate eye. The country, which still lacks green, seems dotted everywhere with white-satin pavilions. 'Twould be a callous heart indeed that could resist the magic of this awakening.