More liquid enters the membrane than issues from it; consequently the internal pressure increases until it is great enough to break through the membrane, somewhere allowing a drop of the liquid which is a solution of metallic salt to escape. On account of the chemical decomposition, this drop immediately surrounds itself with a new skin, and the process of rupture and reformation is repeated until the metallic salt inside the membrane is completely decomposed. We thus see arising under our eyes in a few minutes a marvellous arborescent structure which could at first sight be taken for some plant of inferior order. The rupture of the membrane always takes place in the most recently formed portion, because there the membrane, which thickens gradually, has as yet the least thickness; that is generally the upper portion, so that this offers another analogy to plant life. The coloration of the cells differs with the nature of the metallic salt, but we cannot trace any influence upon the forms obtained. By throwing into the solution several different metallic salts, one can form a many-coloured garden in a small bottle. We are far from seeing in this experience anything but a quite external resemblance to the phenomena of living matter. Yet it leads us to other reflections, especially as we do not yet know anything concerning the real nature of living matter. Among plants and inferior species of the animal world we cannot imagine a life conscious of itself. But in common with our silica creature they show growth and the consumption of chemical substances. In both cases that growth is arrested wherever and whenever the food gives out. This happens in the silica solution when the provision of metallic salt is exhausted; and these are not the only analogies which one can find. But it will be said that there is in reality a capital difference: in one case we have to do with real life for which we have no explanation; in the other we have to do with a simple chemico-physical phenomenon. We reply that a few centuries ago this chemical vegetation would have been an enigma as life itself is still to us, and nobody would then have doubted that he was observing the development of some strange plant. Would they not then have taken the silicon cell for an organic cell? What follows? That the idea of living nature is quite relative, that it changes with our knowledge, and that an imaginative spirit is quite at liberty to endow the stare which we just excluded from life with a life quite different from ours. Apart from these possibilities, the somewhat discouraging result of our previous study was that of all celestial bodies visible to us only two or three could be described with any probability as fit to support something resembling our terrestrial organic life. We cannot object to this conclusion so long as we take it literally, but we wish to point out that all depends upon the little restriction contained in the words “visible to us.”