"The doctrine of idols bears the same relation to the interpretation of nature as that of sophisms does to common logic. It is the peculiar and perpetual error of the human understanding to be more moved and excited by affirmations than by negations; whereas it ought duly and regularly to be impartial; nay, in establishing any true axiom the negative instance is the most powerful." - FRANCIS BACON. LECTURE I INTRODUCTORY In this course of lectures I shall give, on many questions, the Scotch verdict of "not proven," and experience warns us that this will be interpreted as an assertion that they are proved or disproved, although no one can, in justice, interpret an admission that a thesis may some time be proved or disproved as belief that either of these things will come about, or as an admission of anything else except a suspension of judgment, for all must hold it the height of folly to found a scientific opinion on lack of evidence. If I sometimes speak of things that are not commonly held to fall within the province of zoology, — if I try now and then for soundings in waters which able pilots tell us are far out of the course of our ship, — I hope they who follow me to the end of our voyage will admit that I have not wandered from our true course; although it may be well to show now, by way of introduction, how it is that zoologists find themselves face to face with many problems which other men of science have agreed to lay aside as insoluble or irrele vant. I shall try to show that life is response to the order of nature in fact, this thesis is the text of most of the lectures; but if it be admitted, it follows that biology is the study of response, and that the study of that order of nature to which response is made is as well within its province as the study of the living organism which responds, for all the knowledge we can get of both these aspects of nature is needed as a preparation for the study of that relation between them which constitutes life. Our interest in all branches of science is vital interest. It is only as living things that we care to know. Life is that which, when joined to mind, is knowledge,knowledge in use; and we may be sure that all living things with minds like ours are conscious of some part of the order of nature, for the response in which life consists is response to this order. The statement that physical phenomena are natural seems to mean little, but the phenomena of life are so wonderful that many hesitate, even at the present day, to believe that nature can be such a wonderful thing as it must be if the actions of all living things are natural; and, as I shall try to find out in this course of lectures what we mean by the assertion that living nature is natural, I shall now attempt, by a few illustrations, to give a broad outline of some of the most notable features of the nature of living things. The outer surface or shell of a crab is an excretion that is formed once for all; for while it may stretch a little at the joints, it does not grow, and as the living body must in time become too large for it, new shells, one size larger, are formed from time to time under the old one, which is then thrown off. The frequency of these moultings conforms to the rate of growth. The little crab sheds its shell either before or a few minutes after it is hatched from the egg, and a second moulting takes place within forty-eight hours, but the next interval lasts four or five days, and each successive shell remains useful for a longer time, until a mature crab may pass a year or even longer without moulting. The process is natural or mechanical, for nothing the crab can do for itself retards or hastens its growth or the secretion of a new shell; nor can any part of the process be attributed to its own actions, except so far as these actions are due to its nature, although it will not grow unless it seeks and finds food, nor will the old shell take itself off, unless the crab draws its limbs out by bodily movements which are both complex and violent. Many enemies, man and the hard crab among them, prize the soft crab as a palatable delicacy, and as it is helpless and defenceless while moulting, and until the new shell has grown hard, the crab hides under the sand or among the grass of the marshes until the dangerous crisis is past. No one can say whether the crab is or is not conscious of its danger, or whether it hides voluntarily or involuntarily, but as no crab which has not escaped its enemies at the moulting season now survives, all the modern edible crabs hide by nature, just as they grow and shed their shells by nature. Some crabs pass |