It seems that every individual of every separate kind has power to form certain shapes, with certain markings, and no more. It is as if upon each minute speck of vegetable life had been originally impressed its own--not _individual_ character, but _class_ character. This character unconsciously expresses itself in such and such a form of shell, just as with men the individual character expresses itself in such and such outlines of face. The same may be said of Foraminifera and Radiolarian shells. Some Diatoms have a singular power of movement; and from this sprang early mistakes, through which they were wrongly classed as animals. Many of them grow, like ordinary plants, fixed in one spot. But many others are in continuous and regular motion. Careful study has, however, made it clear that the movements of Diatoms are purely mechanical, purely involuntary, like those of some sensitive land-plants. It is probably due to the working of food, taken into the little organism, and not obedient to any _Will_ on its part. It may be that herein lies the great difference between a Diatom and a Foraminifer. The one exists, but has no approach to consciousness; or, at least, probably no approach to any power of choice. The other, though of the very lowest and feeblest type of Animal-life, may yet be supposed in its infinitesimal measure to have a _wish_, and to be able to act upon that wish. But here we do not get beyond conjecture. Where Life exists, it _may_ be that in all cases some dim form of consciousness exists also, which _may_ involve some faint power of choice. Flint-making, like Chalk-making, is not only an old-world and long-past operation, but a present one. Diatoms lived and died in ages gone by, and their remains are found hardened into flint. Diatoms live and die in these days; and their remains may yet, in centuries to come, be transformed into the same substance. From Diatoms one might range upward through an enormous variety of Ocean-weeds, of all kinds and descriptions. Though they are the “last and lowest of all the tribes of plants,” yet it is a wide step from the undermost to the uppermost of even this humble Vegetable Tribe. At least five or six thousand species of Sea-weeds are known to Naturalists. Each ocean, each lesser sea, has its own particular vegetation, largely affected by the varying degrees of saltness, the warmth or coldness of the water, and the faster or slower currents which happen there to prevail. Sea-weeds of all sizes are found, from the invisible diatoms to enormous growths in Pacific waters, reaching to yards upon yards in length, with solid trunk-like stems, and huge fronds like those of a tropical palm.