THE FORMATION OF VEGETABLE MOULD

Otago Witness, Issue 2690, 4 October 1905, Page 77

THE FORMATION OF VEGETABLE MOULD

THROUGH THE ACTION OF WORMS: WITH OBSERVATIONS ON THEIR. HABITS.

By Chaki.es Darwin, LL.D., F. 8..5.

(Thirteenth Thousand. With Illustrations.) Reviewed by Dinorxis. London: John Munay. Dunedin : Whitcombe and Toombs. 3s.

Nothing can be too insignificant for the attention of the wisest which is not too insignificant to give pleasure or pain to the meanest. — Bacon.

When, about a quarter of a century ago, Charles Darwin sent tha miuwnscript of this book to the printer, he had no idea that it was to prove one of the most popular of all lus works. To him it was merely "a curious little book," about the publication of which he had soma misgivings, although it contained tbe results of observations and experiments made during a lai'ge part of his lifetime. In this singularly fascinating and interesting monograph tha great naturalist took in hand one of the lowliest and 1 humblest of living forms, the common earthworm, a-nd by an exhaustive study of its habits and manners strove to show how tlie entire existence of vegetable mould — t.foe ordinary covering of fertile soil upon the- face of the carth — is due to the long but unobstrusive action of these little-noticed and ever active architects. By the acids which they evc-lve he showed that they aid largely "in the disentegration of the shone beneath the. surface; that by their constant practice of eating fallen leaves, -which they drag down with 1 them into their burrows, they produce the fine eastings of soft earth so familiar to everybody, and thus reinstate the coating of humus above the bare rock as often as it is washed away again in the course of ordinary denudation by the rain and the torrents.

It is true that subsequent investigation has shiowin the possibility of vegetable mould existing under certain conditions without the intervention of worms to any marked extent ; but, as a whole, there can be- little doubt that over most parts of the world the presence of soil, and therefore of the vegetable growth rcoted in it, is entirely due to the unsuspected yet ceaseless activity of these humble but primeval and important tillers of the earth.

The amount of -work dicfna by jworms is prodigious, and its value of tbe utmost importance. Worms live chiefly in the superficial mould, which is usually from 4m or sin to lOin, and even 12in, in thickness, in the cultivated parts of Britain and other countries. It is this mould which passes over and over again through their bodies and is brought to- the surface. Worms occasionally burrow deeply into the subsoil, bringing up new material, which ultimately goes to increase the surface layer of mould. It is hard to say how thick this layer would become in coiirse of ages but for the opposing a,gencies which denude it — rain, wind, etc., — while much of the net lesult is lost by being washed down by rivers and deposited on the ocean floor ; an the other hand rich pockets of soil are commonly formed in lnollo'tts, and the proceeds of water denudation are in some cases .accumulated in deltas, forming fertile tracts often of marvellous productiveness. In some great forest regions free from denuding agencies deep beds of extremely rich humus have been, formed by the action of earthworms solely, but in general the actual amount of soil is not largely increased by them. Their chief work consists in sifting the finer from the coarser particles, mingling the whole with vegetable debris, saturating it with their intestinal secretions, and continually freshen, ing the surface, by means of their castings. Darwin's calculations, made with all his characteiistic painstaking, led him to conclude that 15 tons of castings were annually thrown up on a<n> acre of ordinary land in England. In some places there is little reason to doubt that the quantity is much greater. No reader of this absorbingly interesting little book could fail to be impressed by the cumulative importance of separately infinitesimal elements as illustrated by the achievements of the timid, shrinking, blind, and somewhat dull-sensed earthworm.

A most interesting cb^ter is that which tells of the part played by earthworms in the burial and preservation of ancient buildings. At Abinger, Silchester, Wroxeter, and many other places in Britain Where Roman remains have been excavated careful measurements and observations were made either by Darwin or his friends, the results, as given in the text and in a &erie.s of beautiful diagrams, being most surprising. At Abinger, not far from Damon's own home, a villa, of RomanBritish age was uncovered, the vegetable mould forming tho upper layer here being from llin to 16in in depth. It is considered likely that these buildings had been destroyed and deserted 1400 or 1500 years ago, and gradually covered over by the castings- of worms until not a trace of ilwm was visible upon the surface.

Truly, as the author says, "archfeologists are probably not aware how much they owe to worms for the preservation of many ancient objects. Coins, gold ornaments, stone implements, etc., if dropped on the surface of the ground, will infallibly be buried by the castings of worms in a few yeais, and will thus be safely preserved until the land at some future time is turned up. Among striking instances of this kind, the ploughing of a grass field near Shrewsbury yielded a surprising number of iron arrow heads. These were believed by antiquaries to be relics of the battle of Shrewsbury in the year 1403, which had been originally left strewed on the battlefield." . Ido not know if tlie huuters-up of Maori

weapons, etc., have acted on this hint, but it is worth noting, especially as a good corroborative instance is given as showing that "worms appear to act in the same maner in New Zealand as in Europe." I The late Sir Julius yon Haast, in tho "Transactions of the New Zealand Institute," describes a section near the coast, consisting of mica-schist, covered by fiva or six feet of loess, above which about 12 inches of vegetable soil had accumulated. Between the loess and the mould there was a layer from three to six inches in thickness, consisting of 'cores,' implements, flakes, and chips, all manufactured from hard basaltic rock. "It is therefore probable that the aborigines, at some former period, had left these objects on the surface, and that they had afterwards been slowly covered up by the castings jof worms." There may be many another deserted Maori arsenal lying unsuspected j under similar protection. As most people know, earthworms ar» I nocturnal animals, seldom leaving their burrows by day when undisturbed. In addition to studying them in their natural haunts, Darwin kept numbers of earthworms in flower pots for purposes of closer observation and experiment. The amount of light he throws upon the intelligence and habits of these- earliest of all agriculturists is simply marvellous. As an oldtime reviewer remarks : — "In the eyes of most men . . . the earthworm is a, m«re blind, dumb, senseless, and unpleasantly flimy annelid. Mr Darwin undertakes to rehabilitate h : s character, anl the earthworm steps forth at once as an intelligent and benificent personage, a worker of vast geological changes, a planer down of mountain sides ... a friend of man . . . and an ally of the society for the preservation of ancient monuments." T.his is the book of an animal whoso doings have, without doubt, an intimate and extremely important bearing upon human welfare — a ceaseless 'toiler, whose labours have done more to give to the earth its beauty and fertility than any other creature. I fear what"l have said of it gives but a poor idea of the scope of the work, which is one that ghoul's be in the hands of every nature-lover. Darwin was great in many ways, but greatest of all as a teacher. He loved mercy, and the taking of life was always abhorrent to him. In this book he shows how close and constant study of living things may be carried on indefinitely without injury' to its subjects. Like Cowper, we feel that he would not number in his list of friends "the man who would, needlessly, set foot upon a worm."