the earth a new mass is formed out of the two-the earth and the meteor-which had before existed apart. On the other hand, it has been thought possible, some think it has been proved, that meteors were originally projected from the sun or planets--if so, every such case was an illustration of the process of segregation; masses which had before formed a single mass, and had shared the same motions in reference to other masses, being thrown apart to move thenceforth for a longer or a shorter period of time (in some cases for ever) independently of each other. If Mr. George Darwin's views are correct, and our moon was at any time separated either in a single mass, or, as I think more probable, a ring of small masses, from the earth, that was a process of dissolution, or, rather, segregation. So also with the other satellite systems, and with the rings of Saturn, if they were really formed in the way suggested. In the latter case these rings illustrate at the same time both processes; for while they were on this hypothesis expelled from Saturn and so illustrate segregation, their component small masses are gathering together to form hereafter a single moon, or it may be two or three moons, and thus illustrate aggregation.

But to show the generality which characterises Mr. Spencer's theories we may here take an illustration of a quite different character. In the growth of a nation out of tribal races which had been pursuing each a separate existence, nomadically traversing a continent before they settled down to occupy a country, we have a process of aggregation; in the growth of colonies formed out of groups of persons who have left their country at different times and with diverse aims and purposes, we have also a process of aggregation in one aspect, for these colonies are formed by the aggregation of groups before moving apart; but in a wider aspect we have segregation, each colony being separated by the removal of parts from what had before been one whole nation. Where a colony is formed of groups from several nations there is, in reference to the colony, a predominant aggregation of matter and dissipation of motion; where one nation forms several colonies there is, in reference to the nation, a predominant segregation of matter, and assumption of motion.

But, in fact, as these processes take place throughout the universe in general and in detail, we might select our illustrations from a thousand different sources; we might view matters on a very large scale or on a very small scale, or on a scale having any position between these extremes.

The third and fourth statements of Mr. Spencer's philosophy run thus:

3. Evolution is simple when the process of integration, or the

formation of a coherent aggregate, proceeds uncomplicated by other pro

cesses.

4. Evolution is compound when, along with this primary change from an incoherent to a coherent state, there go on secondary changes due to differences in the circumstances of the different parts of the aggregate.

The explanation of 2 leaves little to be explained here. The reader must note carefully, however, that the word evolution here has that limited and incorrect sense in which it has already been used in statement 2. It means here the process of formation of a coherent aggregate out of matter which had before been scattered more or less sparsely. Probably no illustration can be given from nature of an absolutely simple process of aggregation, any more than illustrations can be given from nature of perfectly straight lines, circles, ellipses, and so forth. The philosopher may speak of simple evolution and define it, just as the Newtonian may speak of motion in a circle around a central attracting mass, but as a matter of fact no such evolution can take place. In every instance of change from an incoherent to a coherent state, that is, from the condition of matter more or less scattered to matter forming a single aggregate, changes arising from the different circumstances of the different portions of aggregating matter must in every case occur. From the nebulous mass aggregating into a system of suns, down to the aggregation of the minutest drop or vesicle of fluid from vapour, or even in all probability down to the formation of molecules out of atoms (only no one knows what atoms or molecules in reality are), there must be varieties of condition in the forming mass causing differences of constitution in the mass formed; at any rate, I find myself unable, after long study, to think of any case in which an absolutely uniform process of aggregation takes place or can ever be conceived to take place. Of compound processes, of course, the illustrations are endless. Those we have already considered will serve as well as any others. Every process of formation, or of what Mr. Spencer here understands by the word evolution, must of necessity be varied in different parts of the forming aggregation by varieties in the conditions under which the formative process is applied to different parts of the aggregating material. Whether it be a stellar system forming out of star mist, or a solar system out of meteoric and cometic matter, or a single sun or other celestial body out of multitudinous bodies before discrete,-or, again, whether the aggregation is utterly unlike any studied by the astronomer, as the aggregation of a nation. out of many races, or the formation of a society of any sort from scattered and before unassociated individuals, or the growth of an

animal by the slow building together of material particles drawn from many sources, or the development of a race of animals by any process of evolution: in every case, the various parts of the aggregate must differ inter se, because of the varying conditions under which they are severally formed.

5. These secondary changes constitute a transformation of the homogeneous into the heterogeneous-a transformation which, like the first, is exhibited in the universe as a whole and in all (or nearly all) its details; in the aggregate of stars and nebulæ, in the planetary system; in the earth as an inorganic mass; in each organism, vegetal or animal (Von Baer's law otherwise expressed); in the aggregate of organisms throughout geologic time; in the mind; in society; in all products of social activity.

This amounts to the statement that processes of aggregation, affected as they are by varieties of condition, result in variety of structure. I venture to object to the statement that the homogeneous is transformed into the heterogeneous, because it implies that homogeneity can for a time (however brief) exist. This is contrary to experience. The process which actually takes place is a transformation from the less heterogeneous to the more heterogeneous, the strengthening and stronger marking of varieties of structure which began with the very beginning of the forming aggregation. Absolute uniformity never has existed or can exist in any part of the universe, large or great, any more than any absolute physical entity can exist which answers to the geometrical definition of a straight line. But the importance of the proposition before us is not modi fied by this necessary change. It remains true that, in the processes by which coherent aggregates of any sort whatever, and on whatever scale, are formed out of materials before separate and discrete, varieties which began at the very outset of the process become more and more marked as the process continues.

As an illustration, consider the formation of the solar system. We need not trouble ourselves to decide between the various theories which have been formed as to the actual way in which the solar system came into existence. Suffice it that whether the system was formed by the contraction of a mighty mass of nebulous matter, or by the aggregation of meteoric matter, the circumstances under which the planetary scheme came into existence were originally such that the growth of some- -as of Jupiter and Saturn-was encouraged, while others, like Mars, Mercury, and the asteroids, acquired bulk and substance with difficulty. From the beginning the former planets were doubtless the larger; and as time went on, their absolute, and probably VOL. CCLIV. NO. 1825.

G

their relative, superiority increased, until at length they came to occupy their present position; that is, to use the technical language which seems unfortunately coming into vogue in this subject, they became differentiated from the minor planets by their marked superiority in bulk and mass.

The law thus recognised prevails everywhere throughout the universe, in general as in detail. It is the physical form of the law, 'To him that hath shall be given, and from him that hath not shall be taken even that which he seemeth to have.' Thus, in the case just considered, to the planets which had large bulk and mass, greater bulk and mass were given, while those which were smaller, lost, through the relative slowness of their growth, even that position which originally no doubt they seemed to have as members of a family of bodies not altogether unlike, and fell into a different and (so far as age is concerned) an inferior class. It is the same in all cases of systematic evolution. We are thus led to the law indicated in Mr. Spencer's next statement, the wording of which, like that of some which follows, is not altogether calculated to invite the attention of the unscientific reader, though the subject matters of Mr. Spencer's philosophy are such that all should understand its general purport.

6. The process of integration, acting locally as well as generally, combines with the process of differentiation, to render the change described in 5, not simply one from homogeneity to heterogeneity, but from an indefinite homogeneity to a definite heterogeneity; and this trait of increasing definiteness, which accompanies the trait of increasing heterogeneity, is, like it, exhibited in the totality of things, and in all its divisions and subdivisions, down to the minutest.

In plain English this might be expressed somewhat as follows :-When a whole is forming, the various parts not only differ because they are formed under different conditions, but because the formative process itself (acting in the various parts as well as in the forming mass or system as a whole) tends to produce different results in different parts. Thus not only is the product varied in character in its different parts, but the differences are definite. There is not an indefinite gradation from one form to another, but distinct steps of gradation, so to speak,-and this is recognised throughout the universe, regarded as a whole, and in all its parts, and in all the parts of these parts, down to the minutest subdivisions.

For instance, in the solar system, the formation of a single system out of indefinitely distributed and moving matter, led to the formation of a central mass, and of bodies travelling around that mass, distinctly unlike it in character. Among the bodies thus travelling

the formative process, acting diversely in different parts, and having varied quantities of matter and rates of motion to deal with, formed diverse families of bodies, the great planets in one group, the minor planets in another, the asteroids in a third-all definitely distinguished from each other. In biological evolution definite variations, taking their origin at first in minute differences of condition, surroundings, and so forth, separate the various races, animal and vegetable in each race the various genera become similarly distinct, while individual members of the same genus are also distinguished one from the other by peculiarities arising from the different constitutions under which each is formed. The same again is seen in the formation of distinct nations from among the various tribes and races of men, the characteristics which distinguish nation from nation becoming more and more marked as the nations gradually gather coherence, and what may be called national individuality. Within one and the same nation class distinctions arise and become more marked with the progress of time. Within each class minor distinctions come into existence, and separate sub-class from sub-class more and more definitely. Still smaller subdivisions are formed, which in turn become more and more characteristically distinguished one from the other, till we reach the family, and finally the individual members of the family, the limits of subdivision in this direction. And so in every possible case, under all conceivable conditions, on the large scale as on the small, the law holds,--aggregation is inevitably accompanied by the appearance of varieties of condition, quality, &c., in the parts of the aggregating mass, and, as aggregation proceeds, these varieties become more and more marked.

7. Along with this redistribution of the matter composing any evolving aggregate there goes on a redistribution of the retained motion of its components in relation to one another; this also becomes, step by step, more definitely heterogeneous.

As the aggregate is gradually formed, the motion of the matter forming the aggregate is gradually dissipated, as when masses which had been travelling freely around the sun or a planet are one by one brought to rest on the surface of the body whose mass they thus help to build up. But the motion is not altogether lost. It may, as in the case just considered, result in motion affecting the formed mass as a whole-the rotation in this case of a sun or a planet. It may result in systematic movement within the scheme or system thus formed, as in the movements of the planets within the solar system, or of satellites within a system circulating round a planet. But in the Spencerian philosophy motion is used in a