1. Neural changes and habits.

2. Muscular modifications.

3. Consequent modifications of bone. It carries the question no further to say that these are correlated, however loose may be the meaning of that word that is understood. If the prerogatives of Selection within the germ, of segrega­tion of unit-characters and dominance, and of mutations are not unlimited in the construc­tion of organisms, there still remains a sphere of action for the initiating power of the nervous system. Bones grow and change their form in response to increased or altered muscular action on them, and it is necessary to look back a stage further in the story to the neural changes however produced. There have been abundant opportunities in the long history of mammalian evolution for primitive forms to take a new course of life, and they have done so on an extensive scale. The impulses that have led them may have been started by some “needs” such as Lamarck taught, some change in their surroundings involving new stimuli, or “insults,” as Haeckel called them, but the first of the structural stages must have been in the cerebral cortex.

Cross-Roads in Evolution.

The most instructive levels of animal evolution are those where two or more great stocks have diverged from a primitive one. There may have been several factors leading to the division of the early Ungulates into the odd-toed and even-toed groups, of the Carnivora into cats, dogs and bears, the Felidæ into the highly-specialised genera of that intense family, the early parting of gibbons from the common anthropoid stem, and then the division of this line into the three great genera with which we are familiar. Whatever may have been the unknown factors in the environment such as changes of climate and level, geographical isolation, increase of foes, profusion or lack of food, to which these diverging stocks became adapted in their organs and form, in fact whatever we do not know, we know this—that in their measure they acquired more convoluted and often larger brains, and the stimuli passing through their receptors into their consciousness increased with an everflowing tide, in volume, intensity and complexity. Many an archaic habit of their race they must unlearn, and it is doubtful if germinal selection would avail in this valuable process of economy as it is held to do in the case of the human little toe.

It may be taken as granted that increasing complexity of brain in their own lines of life did accompany these adventurers of small or large groups. It follows that muscular changes from the original stock would follow neural changes, for movement and activity is inseparable from the animal, and the integrating action of the nervous system would constantly initiate, maintain and establish fresh habits and these be expressed in new muscular structure. Whatever higher uses, as we believe them to be, man makes of his brain, as reflec­tion, reasoning, imagina­tion and associa­tion, such were not the new properties acquired by these adventurers. They were very much concerned with hunger and love, and for them “philosophy” did not sustain the structure of their world. But more varied movements of head, trunk and limbs, and greater agility and strength brought them such prizes as were within their reach. This may be only another way of expressing Sir E. Ray Lankester’s concep­tion of educability, which he maintains to be the only acquired character the organism inherits, and it may be therefore assumed to be under the iron law of selection. This must be accepted with the respect due to the high authority from which it proceeds. But such a concep­tion, while it removes a false light in certain regions, sheds no light on the pathway of animal evolution, unless modifications be transmitted, and we can now take it that man does not inherit the power to speak which for incalculable ages he has been learning, nor to write, even though in the days of the early Pyramid-builders and the Sumerians in the plains of Chaldea they possessed the power of writing, nor can a musician’s child learn to play an instrument without teaching, or indeed man perform any of his arts and crafts by second nature: so, negatively, this knowledge is valuable, and the neo-Lamarckian must proceed on his quest without anything more than educability to aid him—but it will serve. The fact is that we do not inherit habits or associations as such at all, but the neurones of the grey matter in spine and brain which subserve, direct and control them. Though a fresh neurone or two in the brain of an early ungulate deliberating, so to speak, as to the life he shall take up, whether that of oxen or horses, may be trifling in itself as to immediate value to the animal, it may be to him as much a matter of fate to acquire those microscopic cells as it was to the undifferentiated organism that paused before it sealed its fate as plant. Under the free and enlightened government of the integrating nervous system liberty to express itself to an almost unlimited extent, in accordance with progress, is thus open to the hypothetical adventurers.

When considering such an aspect of the organism as the “choice” between the career of an odd-toed or even-toed ungulate, a cat or dog, a lion or tiger, a gibbon or other of the four anthropoid genera which assuredly was presented to certain groups of primitive ungulates carnivores, felidæ or apes, as historical beings, the vision of the process is sore let and hindered by the limiting force of certain expressions which have been sanctioned with the imprimatur of fifty years’ high thinking in the realms of high biology. I refer of course to the terms Selection and Evolution which, though they cannot be replaced by better terms, have the power and sometimes have had the effect of impressing on the story of organic existence an aspect of determinism which does not allow, for any purposive action of the individual, the working out of its own salvation, on the part of higher forms at any rate. As among nations self-expression has become of late a powerful force in their development, and indeed of individuals, so it may be argued by analogy that the total experience of an organism, may result in its co-operation in the process of its progress towards higher things. Bergson hints at such a process in organisms, but appears to allow nothing for the individual in his élan vital, where the mass alone counts. So if the two binding terms of Selection and Evolution must be granted their enormous power over our thoughts, there must be also a loosing as well as a binding, and we, as well as certain young ecclesiastics in a hurry, may put in a plea for Life and Liberty. Thus is Lamarckism immortal, and the integrative action of the nervous system supplies the reason.

This well-worn subject is not out of place here, where I am trying to show evidence of self-expression in terms of muscular modifica­tion arising from fresh activities of the brain.

New Muscles.

If it can be said without fear of question that “the differentia­tion of muscle and nerve is the morphological result of division of labour, whereby the unit of protoplasm, in which irritability and contractility are combined, has, on the one hand, become modified into muscle, which retains the property of contractility, and on the other into nerve, which retains that of irritability,”[73] and if Wolff’s Law of Bone Transforma­tion teaches that if a normal bone is used in a new way its structure and form will change to meet its new function, which Sir Charles Bell had more vaguely taught in 1834, it cannot well be denied that at certain turning-points in the history of animal organisms the sequence of changes which arise is neural change, muscular modifica­tion and finally change of bone, whether ungulates, carnivores, felidæ, gibbons or big anthropoids or man, be the dramatis personæ. The only question is whether selection or use and habit initiates the subtle and slow process.