besets the real differences between one speck of protoplasm and another and apparently similar speck.

But our want of knowledge of such points may not leave untouched the primary question concerning the nature of life, to which all the properties and qualities of protoplasm, all the varied forms and faces of living beings, are due. On the contrary, it is possible by analogy to arrive at some broad views concerning the nature of life at large, and to such considerations we may now shortly attend. Physiology points out to us that the properties of protoplasm and all its powers of being and becoming are resident within its own substance, and are dependent upon the energy of which it is the seat. Supply appropriate conditions, and the forces of the protoplasm will convert the primitive germ into the form of its progenitor. There is a transformation of force and matter of one kind, into force and matter of another kind therein involved. Such facts point to material powers and forces resident in, and peculiar to, protoplasm as the prime movers of the changes and developments that substance undergoes. As clearly, too, does the transmission of parental likeness from generation to generation argue for the existence of some material and physical basis for the carriage, by the protoplasm-germ, of the features of the species. If so much be admitted, it seems illogical to deny that whatever properties the protoplasm of germ or adult exhibits depend, strictly speaking, upon the chemical and physical properties of that substance. Thus we approach the idea that this mysterious "life,” which no one has yet successfully defined-for the plain reason that the terms of the definition are unknown-simply represents the sumtotal of the energies of the physical, chemical, and other properties of protoplasm. Nowhere do we find life dissociated from protoplasm; and this fact alone argues in favour of the view that the "vital force" of the scientist or the "vital spark" of the poet, is in each case merely the convenient and summary expression of that high form of energy, which corresponds to no one force in nature, but to all combined.

If this hypothesis be deemed essentially materialistic-as unquestionably it will be from certain points of view-its supporters still possess a distinct coign of vantage in a simple and logical appeal to the facts and phenomena of nature and life as they stand. In addition to the pregnant fact just mentioned, namely, that life requires for its exhibition a material basis seen in protoplasm, the mere considerations that this substance is composed of no unknown elements, but of well-defined and common substances, and that its composition is not ethereal but material, support the view that life is no mysterious aura, but a collocation of the forces and energies and of the material substances which make protoplasm. Life is a property of protoplasm-such is the latest product of scientific thought and research. The forces which make protoplasm are regarded as those

which make life; and although the exact relationship of these forces is as yet unknown, analogy leads us to believe that they are not materially different, if they are different at all, from those which have made the world of inorganic matter what it is. It is analogy, too, which reminds us that certain forces produce, under combination, very different results from those which they exert when acting in separate array. The relationship and correlation of the physical forces not merely teems with examples of such results, but leads us to think of the possibility and probability that life remains a mystery to us simply because the terms under which its component forces are combined are as yet unknown. In any case, we require to postulate a "lifeforce" of one kind or another. It remains for us to choose between the "vital force" of former decades of biology-a term committing itself to no explanation of vital phenomena whatever—and the idea that in the properties of protoplasm-derived whence and how we, as yet, know not-we find the true nature of life.

But analogy rests not here. An extension of thoughts like the foregoing leads us towards the world of inorganic matter with the view of inquiring whether there exist any links or connections between that lifeless universe and the living world which claims protoplasm as its universal substratum. The forces which act upon the lifeless world are those which also affect animals and plants; but the latter are enabled to resist, alter, and modify the action of these forces in greater or less degree, whilst lifeless matter exists and is acted upon without response. Otherwise, however, the phenomena of the inorganic world, despite their sharp demarcation from the phases of life, may be regarded as presenting us with many facts of origin as inexplicable as those exhibited by living beings. It has well been remarked that the growth of the crystal, taking place in virtue of physical laws, to attain an exact and unvarying form, is as mysterious as the growth of the tree; and that common salt should crystallise in the form of the cube is as profound a mystery as that an acorn should become an oak, or another protoplasmic germ evolve the human form. If we are to assume that the forces which rule the world of life are inexplicable simply because they are living forces, it might equally well be maintained that the inorganic world and its ways should be the subjects of similar mysticism. Far more rational, because more likely to be true, are the ideas which lead us to note in the living world the highest term to which matter may attain. As the living world is dependent on the non-living for its support, as we are both in the earth and of the earth, so may we conceive that the forces which mould the world, which disperse the waters and rule the clouds, have contributed in their highest manifestations to combine matter into its most subtle combinations in the form of the animal and in the guise of the plant. Huxley's words

are worth weighing when he says: "It must not be supposed that the differences between living and non-living matter are such as to bear out the assumption that the forces at work in the one are different from those which are to be met with in the other. Considered apart from the phenomena of consciousness, the phenomena of life are all dependent upon the working of the same physical and chemical forces as those which are active in the rest of the world. It may be convenient to use the terms 'vitality' and 'vital force' to denote the causes of certain great groups of natural operations, as we employ the names of 'electricity' and 'electrical force' to denote others; but it ceases to be proper to do so if such a name implies the absurd assumption that either electricity' or 'vitality' is an entity playing the part of an efficient cause of electrical or vital phenomena. A mass of living protoplasm is simply a molecular machine of great complexity, the total results of the working of which, or its vital phenomena, depend, on the one hand, upon its construction, and on the other upon the energy supplied to it; and to speak of 'vitality' as anything but the name of a series of operations, is as if one should talk of the 'horologity' of a clock."

Although research has not placed the puzzle of life and its solution. at our feet, our inquiries have at least served to indicate the direction towards which modern scientific faith is slowly but surely tending. The search after a material cause for phenomena, formerly regarded as thoroughly occult or supernatural in origin, is not a feature limited to life-science alone. Such a characteristic of modern research indicates with sufficient clearness the fact that, as biology and physics become more intimately connected, the explanations of the phenomena of life will rest more and more firmly upon a purely physical and appreciable basis. That life has had a distinct beginning upon this earth's surface is proved by astronomical and geological deductions. That life appeared on this world's surface not in its present fulness, but in an order leading from simple forms to those of an ever-increasing complexity, is an inference which geology proves, and which the study of animal and plant development fully supports. That the first traces of life existed in the form of protoplasmic germs, represented to-day by the lowest of animal and plant formsor rather by those organisms occupying the debatable territory between the animal and plant worlds-is well-nigh as warrantable a supposition as any of the preceding. And last of all, that these first traces of protoplasm were formed by the intercalation of new combinations of the matter and force already and previously existing in the universe, is no mere unsupported speculation, but one to which chemistry and physics lend a willing countenance. Living beings depend on the outer world for the means of subsistence to-day. Is it more wonderful or less logical to conceive that, at the beginning,

the living worlds derived their substance and their energy wholly from the same source? The affirmative answer seems to be that which science tends to supply, with the qualification that, once introduced into the universe, living matter is capable of indefinite self-reproduction, without necessitating any appeal for aid, by way of fresh "creation" of protoplasm, to the inorganic world. As Dr. Allman has remarked, it is certain "that every living creature, from the simplest dweller on the confines of organisation up to the mightiest and most complex organism, has its origin in pre-existent living matter-that the protoplasm of to-day is but the continuation of the protoplasm of other ages, handed down to us through periods of indefinable and indeterminable time." The harmony of these inferences with the doctrine of evolution is manifest. The common origin of animal and vegetable life, and the further unity of nature involved in the idea that the living worlds are in reality the outcome of the lifeless past, constitute thoughts which leave no break in the harmony of creation. "There is grandeur," to quote Mr. Darwin's words, "in this view of life," which, founded upon scientific research, simply commits its supporters to the wholesome philosophic truth, that the ways of all living beings are ordered in conformity with the great system of natural law, whose operation is seen with equal clearness in the formation of a world or the falling of a tear.

THE EVIDENCE

V.

FROM RUDIMENTARY
ORGANS.

IN the exercise of his scientific attainments, there is one aspect in which the naturalist of to-day bears a certain likeness to the detective officer. The latter is perpetually endeavouring to "strike the trail" of the offender through his dexterity in the discovery of clues to the movements of the pursued, and attains his end most surely and speedily when the traces he has selected are of trustworthy kind. The naturalist, on his part, has frequently to follow the history of an animal or plant, or it may be that of a single organ or part in either, through a literal maze of difficulties and possibilities. His search after the relationship of an animal may be fraught with as great difficulty as that which attends the discovery of a "missing heir" or lost relative in actual life; and his success in his mission is found to depend, as does that of the detective's work, simply on the excellence and trustworthiness of the clues he possesses, and on the judicious use to which he puts his "information received." It cannot be denied, however, that modern aspects of science and present-day tendencies in research have largely increased the resemblance between the enforced duties of the criminal investigator and the self-imposed task of the biologist. When, formerly, the order of nature was regarded as being of unaltering kind and of stable constitution, naturalists regarded animals and plants simply as they existed. There was of old no looking into the questions of biology in the light of "what might have been;" because the day was not yet when change and evolution were regarded as representing the true order of the world. When, however, the idea that the universe both of living and non-living matter had an ordered past dawned upon the minds of scientists, the necessity for tracing that past was forced upon them as a bounden duty. With no written history to guide them, the scientific searchers were forced to read the "sermons in stones" which nature had delivered ages ago. Without clear and unmistaken records to point the way, they had to seek for clues and traces to nature's meaning in the structure and development of animals and plants; and, as frequently happens in commonplace history, the earnest searcher often found a helping hand where he least thought it might appear, and frequently discovered an important clue in a circumstance or object of the most unlikely kind.