the movements were twice as great. These observations were made by my son Horace, who will hereafter publish an account of the movements of this stone during successive wet and dry seasons, and of the effects of its being undermined by worms. Now when the ground swells, if it be penetrated by cylindrical holes, such as worm-burrows, their walls will tend to yield and be pressed inwards; and the yielding will be greater in the deeper parts (supposing the whole to be equally moistened) from the greater weight of the superincumbent soil which has to be raised, than in the parts near the surface. When the ground dries, the walls will shrink a little and the burrows will be a little enlarged. Their enlargement, however, through the lateral contraction of the ground, will not be favoured, but rather opposed, by the weight of the superincumbent soil. Distribution of Worms.-Earth-worms are found in all parts of the world, and some of the genera have an enormous range. * They inhabit the most isolated islands; they * Perrier, Archives de Zoolog. expér.' tom. 3, p. 378, 1874. abound in Iceland, and are known to exist in the West Indies, St. Helena, Madagascar, New Caledonia and Tahiti. In the Antarctic regions, worms from Kerguelen Land have been described by Ray Lankester; and I found them in the Falkland Islands. How they reach such isolated islands is at present quite unknown. They are easily killed by salt-water, and it does not appear probable that young worms or their egg-capsules could be carried in earth adhering to the feet or beaks of land-birds. Moreover Kerguelen Land is not now inhabited by any land-bird. In this volume we are chiefly concerned with the earth cast up by worms, and I have gleaned a few facts on this subject with respect to distant lands. Worms throw up plenty of castings in the United States. In Venezuela, castings, probably ejected by species of Urochata, are common in the gardens and fields, but not in the forests, as I hear from Dr. Ernst of Caracas. He collected 156 castings from the court-yard of his house, having an area of 200 square yards. They varied in bulk from half a cubic centimeter to five cubic centimeters, and were on an average three cubic centimeters. They were, therefore of small size in comparison with those often found in England; for six large castings from a field near my house averaged 16 cubic centimeters. Several species of earth-worms are common in St. Catharina in South Brazil, and Fritz Müller informs me "that in most parts of "the forests and pasture-lands, the whole soil, 66 to a depth of a quarter of a metre, looks as if it "had passed repeatedly through the intestines. "of earth-worms, even where hardly any cast"ings are to be seen on the surface.' A gigantic but very rare species is found there, the burrows of which are sometimes even two centimeters or nearly of an inch in diameter, and which apparently penetrate the ground to a great depth. In the dry climate of New South Wales, I hardly expected that worms would be common; but Dr. G. Krefft of Sydney, to whom I applied, after making enquiries from gardeners and others, and from his own observations, informs me that their castings abound. He sent me some collected after heavy rain, and they consisted of little pellets, about 15 inch in diameter; and the blackened sandy earth of which they were formed still cohered with considerable tenacity. The late Mr. John Scott of the Botanic Gardens near Calcutta made many observations for me on worms living under the hot and humid climate of Bengal. The castings abound almost everywhere, in jungles and in the open ground, to a greater degree, as he thinks, than in England. After the water has subsided from the flooded rice-fields, the whole surface very soon becomes studded with castings a fact which much surprised Mr. Scott, as he did not know how long worms could survive beneath water. They cause much trouble in the Botanic garden, "for some of the finest of our lawns can be kept 66 66 in anything like order only by being almost "daily rolled; if left undisturbed for a few days 66 they become studded with large castings." These closely resemble those described as abounding near Nice; and they are probably the work of a species of Perichata. They stand up like towers, with an open passage in the centre. A figure of one of these castings from a photograph is here given (Fig. 3). The |