[Picture: Book cover] THE FORMATION OF VEGETABLE MOULD THROUGH THE ACTION OF WORMS WITH OBSERVATIONS ON THEIR HABITS. BY CHARLES DARWIN, LL.D., F.R.S. THIRTEENTH THOUSAND WITH ILLUSTRATIONS * * * * * LONDON JOHN MURRAY, ALBEMARLE STREET 1904 * * * * * PRINTED BY WILLIAM CLOWES AND SONS, LIMITED, LONDON AND BECCLES. * * * * * CONTENTS. INTRODUCTION Page 1–6 CHAPTER I. HABITS OF WORMS. Nature of the sites inhabited—Can live long under 7–15 water—Nocturnal—Wander about at night—Often lie close to the mouths of their burrows, and are thus destroyed in large numbers by birds—Structure—Do not possess eyes, but can distinguish between light and darkness—Retreat rapidly when brightly illuminated, not by a reflex action—Power of attention—Sensitive to heat and cold—Completely deaf—Sensitive to vibrations and to touch—Feeble power of smell—Taste—Mental qualities—Nature of food—Omnivorous—Digestion—Leaves before being swallowed, moistened with a fluid of the nature of the pancreatic secretion—Extra-stomachal digestion—Calciferous glands, structure of—Calcareous concretions formed in the anterior pair of glands—The calcareous matter primarily an excretion, but secondarily serves to neutralise the acids generated during the digestive process. CHAPTER II. HABITS OF WORMS—_continued_. Manner in which worms seize objects—Their power of 52–120 suction—The instinct of plugging up the mouths of their burrows—Stones piled over the burrows—The advantages thus gained—Intelligence shown by worms in their manner of plugging up their burrows—Various kinds of leaves and other objects thus used—Triangles of paper—Summary of reasons for believing that worms exhibit some intelligence—Means by which they excavate their burrows, by pushing away the earth and swallowing it—Earth also swallowed for the nutritious matter which it contains—Depth to which worms burrow, and the construction of their burrows—Burrows lined with castings, and in the upper part with leaves—The lowest part paved with little stones or seeds—Manner in which the castings are ejected—The collapse of old burrows—Distribution of worms—Tower-like castings in Bengal—Gigantic castings on the Nilgiri Mountains—Castings ejected in all countries. CHAPTER III. THE AMOUNT OF FINE EARTH BROUGHT UP BY WORMS TO THE SURFACE.