In spite of all the differences which a comparison of man with the mammalia presents, should he be classed with them? This question is similar to that which Peysonnel is said to have asked himself, when, struck by the special phenomena presented by the coral, he asked himself whether the object before him was a vegetable.

It is evident that, in order to solve the first problem which arises from a study of the natural history of man, we must have a clear idea what are these great groups of beings, which are called kingdoms; we must give an account of the characters which distinguish and separate them from each other, and then of their true scientific meaning. It will be sufficient for the purpose to explain the well-known laws of Linnæus, supplementing the theory of the immortal Swede by some ideas borrowed from Pallas and de Candolle, and by one of the fundamental conceptions which Adamson and A. L. de Jussieu have almost equally contributed to introduce into science.

II. It is impossible for anyone, whether learned or otherwise, not to recognise at once the difference between two kinds of objects very distinct from each other: inanimate bodies and organised beings. These are the two groups into which Pallas has divided kingdoms under the name of empires. Their distinction is generally easy, and I shall confine myself to recalling some of the most essential differences.

Inanimate bodies, when placed under favourable circumstances, last for an indefinite time, neither taking nor giving anything to the surrounding world; organised beings, under whatever conditions they are placed, only last for a fixed period of time, and, during this existence, undergo every moment losses of substance which they repair by means of materials taken from without. Inanimate bodies, even when they assume the fixed and definite form of crystals, are formed independently of all other bodies resembling them; they have from their commencement fixed forms, and increase simply by superposition of new layers. Every organised being is connected either directly or indirectly

with a similar being, in the interior of which it first appeared in the form of a germ, then grew and acquired its definite form by intussusception.

In other words, filiation, nutrition, birth and death, are so many characteristics of the organised being, of which no trace is found in inanimate bodies. I agree with Pallas in making inanimate bodies compose the Inorganic Empire, and organised beings the Organic Empire.

I must here make an observation, the importance of which will be easily understood.

The existence of the two groups which have been recognised by the good sense of the general public as well as by the science of Pallas, is a fact absolutely independent of all hypothesis. Whatever explanation we may propose to account for the differential phenomena which distinguish them, these phenomena will not the less exist; the inanimate body will never be an organised being.

To attempt, under any pretext whatever, to reconcile or confound these two kinds of objects with each other, is to go in direct opposition to all the progress made for more than a century, and especially during the last few years, in physics, chemistry and physiology. It is inexplicable to me that some men, whose merits I otherwise acknowledge, should have recently again compared crystals to the simplest living forms, to the sarcodic organisms, as they were called by Dujardin, who discovered them, and was the first to give a comprehensive theory of them from minute observations. A change of name is useless; the things remain the same, and protoplasm has the same properties as sarcode. The animals, whose entire substance they seem to form, have not altered their nature; whether monera or amoeboe, these forms are the antipodes of the crystal from every point of view.

A crystal, as M. Naudin has well remarked, closely resembles one of those regular piles of shot which may be seen in every arsenal. It only increases from the exterior, as the pile is increased when the soldier adds a fresh layer of shot;

its molecules are just as immovable as the balls of iron. It is exactly the contrary with the organised being, and the simpler its composition the greater the contrast. The small size of the moneron and the amoeba prevents, it is true, certain observations. I appeal, however, to all those naturalists who have studied certain marine sponges in a living state. They must like myself have remarked the strange activity of the vital whirlpool in the semi-sarcodic substance which surrounds their siliceous or horny skeleton; they will have seen the sea water in which they are placed move with a rapidity which it never exhibits when in contact with any other animal.

The reason is that, in the organised being, the repose of the crystal is replaced by an incessant movement; that, instead of remaining immovable and unalterable, the molecules are unceasingly undergoing transformation, changing their composition, producing fresh substances, retaining some and rejecting others. Far from resembling a pile of shot, the organised being may much rather be compared to the combination of a number of physico-chemical apparatus, constantly in action to burn or reduce materials borrowed from without, and ever making use of their own substance for its incessant renewal.

In other words, in the crystal once formed the forces remain in a state of stable equilibrium, which is only interrupted by the influence of exterior causes. Hence the possibility of its indefinite continuance without any change either of its forms or of its properties. In the organised being the equilibrium is unstable, or rather, there is no equilibrium properly so called. Every moment the organised being expends as much force as matter, and owes its continuance solely to the balance of the gain and loss. Hence the possibility of a modification of its properties and form without its ceasing to exist.

Such are the bare facts which rest upon no hypothesis whatever; and how can we, in the presence of these facts, compare the crystal which grows in a saline solution to the germ which

becomes in succession embryo, foetus, and finally a complete animal? How can we confuse the inanimate body with the organised being.

The two groups are easily separated by the phenomena they exhibit. It is the same with the causes of the phe

nomenon.

Naturalists and physiologists are here divided. Some would have it that the cause, or the causes, are identical, and that conditions, which are almost accidental, alone determine the difference in the results by changing their mode of action. In their opinion he formation of a crystal or of a moneron is only a question of resultant.

Others consider living beings as the result of a cause entirely different from those which act in inanimate bodies, and refer to this cause alone everything which takes place in these beings.

These two methods appear to me, from the exclusive element in each, to be equally ill-founded. It cannot be denied that phenomena identical with those characteristic of inanimate bodies are found in organised beings, and we have, therefore, no scientific reason to attribute them to different causes.

But organised beings have also their special phenomena radically distinct from, or even opposed to, the former. Is it possible to refer all of them to one, or to several, identical causes? I think not. For this reason, I admit with a great number of eminent men of every age and country, and, I believe, with the majority of those that respect modern science, that organised beings owe their distinctive characteristics to a Special Cause, to a Special Force, to Life, which in them is associated with the inorganic forces. For this reason I consider it legitimate to call them Living Beings.

I shall often, however, return to this class of considerations, in order to make it quite clear in what sense I take these words, Force, and Life.

III. The two Empires of Pallas are themselves sub

divided into Kingdoms, which are characterised by special facts and phenomena, becoming more and more complicated as we ascend the scale of nature.

And, in the first place, I distinctly admit with de Candolle the existence of a Sidereal Kingdom. To any one who considers, as far as we are able, the little that we know of the universe, the celestial bodies, suns, planets, and comets or satellites only appear as molecules of the great All which fills indefinite Space. One general phenomenon which is unchangeable, however varied in its forms, is, as it were, the attribute of these bodies. All, whether gaseous or solid, obscure or luminous, hot or cold, move within curves of the same nature, obeying the laws discovered by Kepler. It is now well known that fixed stars do not exist.

In order to explain this phenomenon philosophers have admitted the existence of a force which they have called Gravitation, the effect of which is to precipitate the stars towards one another, as if they mutually attracted each other, whilst obeying the laws of Newton. Now it is well known that the great Englishman himself gave no opinion upon the mode of action of this force, and that he hesitated between the hypothesis of Attraction and that of Impulsion. The first should prevail as being more in accordance with the immediate results of observation; but the second also has had serious partisans, among whom I will only mention M. de Tessan.

Thus Newton, in spite of all his genius, cannot tell us what was the cause of the movement of the stars; he was not even able to determine the immediate mode of action of this cause; and yet there is not a scientific term more universally received than that of Gravitation, there is not a case in which the expression Force is more generally accepted. The reason of this is, that in the presence of general facts and groups of phenomena, it is necessary to make use of terms as simple as possible. We must, however, avoid the delusion of thinking that naming is equivalent to explaining.