The monograph that Gilbert White wished for in 1777 was published by Darwin in 1881, the year before he died-" the completion," he said,

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of a short paper read before the Geological Society more than forty years ago." With his characteristic thoroughness and patience he worked out the part that earthworms have played in the history of the earth, and proved that they deserve to be called the most useful animals. By their burrowing they loosen the earth, making way for the plant rootlets and the raindrops; by bruising the soil in their gizzards, they reduce the particles to more useful, powdery form; by burying the surface with castings brought up from beneath, they have been for untold ages ploughers before the plough, and by burying leaves they have made a great part of the vegetable mould over the whole earth. In illustration of the last point, we may notice that we recently found thirteen midribs of the leaves of the rowan, or mountainash, radiating round one hole like the spokes of a wheel; the withering leaflets had been carried down, and two were sticking up at the mouth of the burrow: that meant 91 leaflets to one hole. Darwin showed that there often are 50,000 (and there may be 500,000) earthworms in an acre; that they often pass ten tons of soil per acre per annum through their bodies; and that they often cover the surface at the rate of three inches in fifteen years. Though our British worms only pass out about 20 oz. of earth in a year, the weights thrown up in a year on two separate square yards which Darwin watched were respectively 6.75 lb. and 8.387 lb., which correspond to 14 and 18 tons per acre per annum.

We follow the work further and it becomes evident that the constant exposure of the soil bacteria on the surface is bound to be important, on the one hand, in allowing them to be scattered by wind and rain, on the other in exposing them to the beneficent action of the sunlightwhich is the most universal, effective, and economical of all germicides.

In Yorubaland, on the West Coast of Africa, Mr. Alvan Millson calculated that about 62,233 tons of subsoil are brought every year to the surface of each square mile, and that every particle of earth, to the depth of two feet, is brought to the surface once in twenty-seven years. It need hardly be added that the district is fertile and healthy.

Earthworms play their part in the disintegration of rocks, letting the solvent humus-acids of the soil down to the buried surface. Their castings on the hill-slopes are carried down by wind and rain and go to swell the alluvium of the distant valleys or the wasted treasures of the sea. The well-known parallel ledges along the slopes of grass-clad hills are partly due to earthworm castings caught on sheep-tracks, and thus we begin to connect the earthworms not only with our wheat-supply but with our scenery. Well may we say, with Darwin: "It may be doubted whether there are many other animals which have played so important a part in the history of the world as have these lowly organised creatures." Those who wish to understand Darwinism should always begin with Darwin's last book-" The Formation of Vegetable Mould through the Action of Worms" (1881). It illustrates the web of life,

the idea of which is essential to an understanding of the struggle for existence and natural selection. But it also illustrates what Darwin had learned from Lyell that great results may be brought about by the accumulation of infinitesimal items. As Prof. A. Milnes Marshall said: "The lesson to be derived from Darwin's life and work cannot be better expressed than as the cumulative importance of infinitely little things."

TERMITES, OR WHITE ANTS.-Henry Drummond, in his "Tropical Africa," tried to make out a case for the agricultural importance of termites, or white ants. It is well known that these oldfashioned insects have a pruning action in the forest, destroying dead wood with great rapidity. Houses and furniture, fences and boxes, as well as forest-trees, fall under their jaws. In some places, “ if a man lay down to sleep with a wooden leg, it would be a heap of sawdust in the morning." But what of the termites' agricultural importance? The point is that they keep the soil circulating by constructing earthen tunnels up the sides of trees and posts and by making huge obelisk-like ant-hills, or termitaries. The earth-tubes crumble to dust, which is scattered by the wind; the rains lash the forests and soils with fury, and wash off the loosened grains to swell the alluvium of a distant valley." It must be noted, however, that Drummond did not prove his case with sufficient precision, and there is, as Escherich points out in his beautiful study of termites,' this difficulty, that, while the castings of earthworms are soft and loose, the earth-tubes and constructions of termites are stony.

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1 "Die Termiten." (Leipzig, 1909.)

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Escherich does, however, admit that the termites have some agricultural importance, and he points out that there are other services to be put to the credit side of their account. They prune off wood that has begun to go; they destroy rotting things, including the bodies of small animals; they make for cleanliness and health. In some low-lying tracts, as Silvestri has shown, there are dry stretches, termite islands," which have been gradually built up from the broken-down remains of termitaries. Nor should it be forgotten that the white ants are often used as food. On the other hand, Escherich does not hesitate to rank them as among the great hindrances to the spread of civilisation. They insidiously devour everything wooden, from the telegraph-post to the wooden butt of the gun hanging against the wall, from books in the library to corks in the cellar. There does not seem sufficiently precise information in regard to the living plants that they attack, and no safe general statement can be made except that their appetite is large and catholic.

With a centre in earthworms, what a variety of interests must be included within the radius of their life and work!-centipedes, birds, moles, seedlings, man. The same is true of termites, and two further illustrations may be given. Observers have reported about thirty different species of termites with the habit of feeding on fungi grown within the termitary on specially constructed mazy beds. The habit is interesting in many ways; for instance, because the fungi afford a supply of nitrogenous material which is scarce in the ordinary diet of wood, and also because a similar habit

occurs in the quite unrelated true ants. Finally, the web is illustrated by the numerous boarders, mostly beetles, that are found in the termitariesnot hostile intruders or parasites, but guests which are fed and cared for apparently for the sake of a palatable exudation with a pleasant, narcotising effect on the termites. With a centre in termites, what a variety of interests must we not include within the radius of their life and work!-fungi and trees, beetles and birds, lizards and ant-eaters, and man more than any.

THE HAND OF LIFE UPON THE EARTH.-The hand of life has been working upon the earth for untold ages. Take plants, for instance. The seaweeds lessen the force of the waves, the lichens eat into the rocks, the mosses form huge sponges on the moors which keep the streams flowing in days of drought. Many little plants are for ever smoothing away the wrinkles on the earth'stheir mother's face, and they adorn her with jewels. Others that have formed coal have enriched her with ages of entrapped sunlight. The grass-which began to appear in Tertiary ages— protects the earth like a garment; the forests affect rainfall and temper climate, besides sheltering multitudes of living things, to many of whom every blow of the axe is a death-knell. No plant, from bacterium to oak-tree, lives or dies to itself, or is without its influence upon the earth. So among animals there are destructive borers and burrowers and conservative agents, such as the coral-polyps and the chalk-forming Foraminifera.

PRACTICAL IMPORTANCE OF A REALISATION OF THE WEB OF LIFE.-What has Darwinism to do with human life? The answer at this stage in