CONTENTS OF No. 477.-OCTOBER, 1923 215 246 Griffith Boscawen 8. AGRICULTURAL POLICY. By the Rt Hon. Sir A. THE QUARTERLY REVIEW No. 477.-OCTOBER, 1923. Art. 1.-THE NEW BIOLOGY. 1. Principles of General Physiology. By W. M. Bayliss. Longmans, 1915. 2. Le Mouvement Biologique en Europe. By Georges Bohn. Paris: Colin, 1921. 3. Tier und Pflanze in intrazellularer Symbiose. By P. Buchner. Berlin: Borntraeger, 1921. 4. Senescence and Rejuvenescence. By C. M. Child. Chicago, 1915. 5. Outlines of Evolutionary Biology. By A. Dendy. Third Edition. Constable, 1923. 6. On Growth and Form. By D'Arcy W. Thompson. Cambridge University Press, 1917. And other works. THERE are various ways in which a science or a department of science may become new. An important discovery may enforce reconsideration of a large range of facts, as in the case of radio-activity or of hormones. A new idea may act as a ferment, like the idea of evolution in biology, or the idea of the conservation of energy in physics. Or the change may be due to a new contact, as when psychology joined hands with physiology. In other cases a transformation has followed the introduction of a new method or a new instrument, as may be well illustrated by the influence of spectroscopy on astronomy, or of microscopy on zoology. But however a science becomes new, the change is organic, like growth or development. It is very rarely that there is anything like casting off a threadbare Vol. 240.-No. 477. garment, or pulling down an edifice and beginning afresh. What happens is more like the re-invigoration of a developing organism. The old is not superseded or discarded, it is re-habilitated or subsumed in a new synthesis. The evolution theory did not depreciate the sound results of comparative anatomy, but it suffused them with light. The discovery of the regulative system of endocrine glands did not replace our conception of the integrative action of the nervous system. What it did was to give the concept of integration new life. One of the central ideas in biology is that of the linkage of lives. It is an old idea, but it was Darwin who made it grip men's minds, for he had the vision of the web of life more vividly than any one before or since. It is characteristic of the new biology that it has set the idea of the correlation of organisms in the centre of its thinking. Nothing lives or dies to itself; everything, as John Locke said, is a retainer to some other part of Nature. Cats have to do with the clover crop in Britain and with the incidence of the plague in India; earthworms affect the wheat supply and water-wagtails the success of sheep-farming. Squirrels do not seem at first sight to have much connexion with the harvest fields, but when they are drastically shot down in the interests of forestry there is a multiplication of wood-pigeons, on whose squabs they levy useful toll, and a wood-pigeon may fill its crop with a thousand grains of oats in the course of a forenoon. The bees and the flowers are hand and glove; the thrush plants the mistletoe and the ants sow the seeds of the broom; the minnow nurses the freshwater mussel, and, by devouring larval mosquitoes, checks the spread of malaria. Long nutritive chains bind organisms together in successive incarnations. The more sunshine in spring the greater is the multiplication of Diatoms and Peridinid Infusorians in the English Channel, and the more these animalcules increase the thicker in the sea-soup is the stock of small crustaceans (Copepods chiefly) on which the daintily-feeding mackerel very largely depend. To make a pound of cod requires ten pounds of whelks; to make a pound of whelks requires ten pounds of seaworms; to make a pound of sea-worms requires ten 2 pounds of organic sea-dust. And so the world goes round! One of the plants most inimical to man's interests is the bracken, for it destroys good pasture and it is so sturdy and insurgent that it can conquer even the heather. The encroachments may be met by laborious cutting and by spraying with sulphuric acid, but it would be more promising to discover new uses for the fern. It makes excellent bedding, it has strong antiseptic qualities, it contains a considerable quantity of potash, and so on. A few experiments have shown that the fish-yield of freshwater lochs can be greatly improved by pitching cartloads of cut bracken into the waters. Their slow decay promotes the multiplication of animalcules, on which small crustaceans and the like depend, and thus the fishes are fed. These experiments should be continued, for it may be that bracken cast upon the waters will return to us in many days in the form of trout. Every one knows that widely separated forms of life are often linked together by being the two hosts of one parasite. Remembering that the sheep and the little water-snail are the two hosts of the liver-fluke, Dr Leiper was able during the War to prove that the very formidable human parasite called Bilharzia spends part of its juvenile life inside freshwater snails. From these the microscopic larvæ pass into the water and swim freely. If an opportunity offers they enter man through cracks and weak spots in the skin. Every third child of the 30,000 born annually in Cairo is infected with Bilharzia, and the parasite is a serious menace to adults as well. Dr Leiper not only traced the lifehistory of the worm, but also has saved thousands of lives by showing that the dangerous intruders can be kept back by good filters, and that the free-swimming stages die within thirty-six hours in water that is kept stagnant. The subtleties of parasitology are often almost incredible. There is a remarkable fluke called Leucochloridium that lives in the intestine of singing-birds on the continent. The microscopic eggs are voided on the meadow and may be eaten by a small snail (Succinea), in whose stomach they hatch. Each larva gives rise to a strange branched form, with ramifications which extend |