sole creator, is at least a most important factor of the beautiful; and therefore the sight of one of these animals is now much more to me, in the respects which we are considering, than it can be to any one in whose memory it is not connected with many days of that purest form of enjoyment which can only be experienced in the pursuit of science.

And here I may observe that the worker in marine zoology has one great advantage over his other scientific brethren. Apart from the intrinsic beauty of most of the creatures with which he has to deal, all the accompaniments of his work are æsthetic, and removed from those more or less offensive features which are so often necessarily incidental to the study of anatomy and physiology in the higher animals. When, for instance, I contrast my own work in a town laboratory on vertebrated animals with that which I am now about to describe upon the invertebrated in a laboratory set up upon the sea-beach, it is impossible not to feel that the contrast in point of enjoyment is considerable. In the latter case, a summer's work resembles the pleasure-making of a picnic prolonged for months, with the sense of feeling all the while that no time is being profitlessly spent. Whether one is sailing about upon the sunny sea, fishing with muslin nets for the surface fauna, or steaming away far from shore to dredge for other material, or, again, carrying on observations in the cool sea-water tanks and bell-jars of a neat little wooden workshop thrown open to the sea-breezes, it alike requires some effort to persuade one's self that the occupation is really something more than that of finding amusement.

It is now twelve years since I first took to this kind of summer recreation, and during that time most of my attention while at the seaside has been devoted to the two classes of animals already mentioned—viz. the jelly-fish and star-fish, or, as naturalists have named them, the Medusæ and Echinodermata. The present volume contains a tolerably full account of the results which during six of these summers I have succeeded in obtaining. If any of my readers should think that the harvest appears to be a small one in relation to the time and labour spent in gathering it, I shall feel pretty confident that those readers are not themselves working physiologists, and, therefore, that they are really ignorant of the time and labour required to devise and execute even apparently simple experiments, to hunt down a physiological question to its only possible answer, and to verify each step in the process of an experimental proof. Moreover, the difficulties in all these respects are increased tenfold in a seaside laboratory without adequate equipments or attendance, and where, in consequence, more time is usually lost in devising makeshifts for apparatus, and teaching unskilled hands how to help, than is consumed in all other parts of a research. From the picnic point of view, however, there is no real loss in this; such incidental difficulties add to the enjoyment (else why choose to make an extemporized grate and boil a kettle in the wood, when a much more efficient grate, full of lighted coals, is already boiling some other kettle at home?); and if they somewhat unduly prolong a research, the full meaning of life is, after all, not exhausted by the experiences of a mill-horse, and it is well to remember that so soon as we cease to take pleasure in our work, we are most likely sacrificing one part of our humanity to the altar of some other, and probably less worthy, constituent.

I may now say a few words on the scope of the investigations which are to be described in the present treatise. To some extent this is conveyed by the title; but I may observe that, as the "primitive nervous systems" whose physiology I have sought to advance are mainly subservient to the office of locomotion, in my Royal Society papers upon these researches I have adopted the title of "Observations on the Locomotor System" of each of the classes of animals in question. It is of interest to notice in this connection that the plan or mechanism of locomotion is completely different in the two classes, and that in the case of each class the plan or mechanism is unique, i.e. is not to be met with elsewhere in the animal kingdom. It is curious, however, that, in the case of one family of star-fish (the Comatulæ), owing to an extreme modification of form and function presented by the constituent parts of the locomotor organs, the method of progression has come closely to resemble that which is characteristic of jelly-fish.

There is still one preliminary topic on which I feel that it is desirable to touch before proceeding to give an account of my experiments, and this has reference to the vivisection which many of these experiments have entailed. But in saying what I have to say in this connection I can afford to be brief, inasmuch as it is not needful to discuss the so-called vivisection question. I have merely to make it plain that, so far as the experiments which I am about to describe are concerned, there is not any reasonable ground for supposing that pain can have been suffered by the animals. And this it is easy to show; for the animals in question are so low in the scale of life, that to suppose them capable of conscious suffering would be in the highest degree unreasonable. Thus, for instance, they are considerably lower in the scale of organization than an oyster, and in none of the experiments which I have performed upon them has so much laceration of living tissue been entailed as that which is caused by opening an oyster and eating it alive, after due application of pepper and vinegar. Therefore, if any one should be foolish enough to object to my experiments on the score of vivisection, a fortiori they are bound to object to the culinary use of oysters. Of course, it may be answered to this that two blacks do not make a white, and that I have not by this illustration succeeded in proving my negative. To this, however, I may in turn reply that, for the purpose of morally justifying my experiments on the ground which I have adopted, it is not incumbent on me to prove any negative; it is rather for my critics to prove a positive. That is to say, before convincing me of sin, it must be shown that there is some reasonable ground for supposing that a jelly-fish or a star-fish is capable of feeling pain. I submit that there is no such ground. The mere fact that the animals are alive constitutes no such ground; for the insectivorous plants are also alive, and exhibit even more physiological "sensitiveness" and capability of rapid response to stimulation than is the case with the animals which we are about to consider. And if anyone should go so far as to object to Mr. Darwin's experiments on these plants on account of its not being demonstrable that the tissues did not suffer under his operations, such a person is logically bound to go still further, and to object on similar grounds to the horrible cruelty of skinning potatoes and boiling them alive.

Thus, before any rational scruples can arise with regard to the vivisection of a living organism, some reasonable ground must be shown for supposing that the organism, besides being living, is also capable of suffering. But no such reasonable ground can be shown in the case of these low animals. We only know of such capability in any case through the analogy based upon our own experience, and, if we trust to this analogy, we must conclude that the capability in question vanishes long before we come to animals so low in the scale as the jelly-fish or star-fish. For within the limits of our own organism we have direct evidence that nervous mechanisms, much more highly elaborated than any of those which we are about to consider, are incapable of suffering. Thus, for instance,