[page] 519

The Formation of Vegetable Mould through the Action of Worms, with Observations of their Habits, By Charles Darwin. With Illustrations. New York: D. Appleton & Co. 1881. pp. 326.

One of the secrets of Mr. Darwin's success in interpreting nature lies in his ability ''to sum up tho effects of a continually recurrent cause," however slight the momentary results may appear.

The means by which he has produced such a marvellous change in modern modes of thought respecting the origin of species are similar to those used with such effect forty or fifty years ago by Lyell to establish a similar principle respecting the action of inanimate forces in geology. The volume before us—the result of forty years of careful observation—would have delighted the author of the 'Principles of Geology,' for it illustrates in a striking manner the enormous geological effects which may be produced by a cause supposed to be insignificant, but which, as usual, turns out to be unnoticed rather than insignificant. Mr. Darwin estimates that there are in gardens 53,767 worms to the acre, and that they would weigh 356 pounds.

Having four or five gizzards apiece, each worm is able to digest a large amount of coarse food, and to eat his "peck of dirt" in a brief space of time. Careful weighing of the "castings" brought to the surface by worms shows that they sometimes amount to sixteen tons per acre annually—sufficient to produce two inches of so-called "vegetable mould" in ten years.

Since worms often burrow to a depth of seven or eight feet, it follows that they may play no mean part in undermining and burying loose stones and monuments of art. Through their agency a field near Mr. Darwin's house has been cleared of cobble stones within his remembrance, and this not so much from the fact that the pebbles have been undermined as because fine earth has been brought to the surface. Many of the foundations of Roman buildings recently discovered in Great Britain are preserved underneath this constantly accumulating deposit of "earth mould," which is from two to three feet deep over the ruins at Wroxeter. We shall wonder if some bold theorist does not soon attempt to account for the prairies of the West as the work of worms, The same action of worms which, in favoring circumstances, covers the surface with humus, in other circumstances promotes denudation, since it exposes the fine earth to the action of both wind and water.

The literary skill of Mr. Darwin appears to special advantage in this volume. He has invested a most unpromising subject with the charm of a romance, his style reminding one of Robinson Crusoe. Children, as we know from experience, read the volume with eager interest, and the philosopher may find much food for reflecting the amount of intelligence described as displayed by an animal so devoid of senses as Mr. Darwin proves the worm to be. Feeling and a faint sense of smell seem the only avenues through which the objects of sense perception penetrate the worm's mind, yet worms show signs of fear, are somewhat social, and have some power of attention; but we are sorry to say they are cannibals.

After perusing the book it is difficult not to share in the enthusiasm of the author's closing paragraph:

"The plough is one of the most ancient and most valuable of man's inventions; but long before he existed the land was in fact regularly ploughed, and still continues to be thus ploughed, by earthworms. 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 organized creatures."