§ 174g. The foregoing criticisms and hypotheses do not, however, affect in any essential way the pre-existing conceptions. If, as in the foregoing chapters, we interpret the facts in terms of that redistribution of matter and motion constituting Evolution at large, we shall see that the general theory, as previously held, remains outstanding.
It is indisputable that to maintain its life an organism must maintain the moving equilibrium of its functions in presence of environing actions. This is a truism: overthrow of the equilibrium is death. It is a corollary that when the environment is changed, the equilibrium of functions is disturbed, and there must follow one of two results—either the equilibrium is overthrown or it is re-adjusted: there is a re-equilibration. Only two possible ways of effecting the re-adjustment exist—the direct and the indirect. In the one case the changed outer action so alters the moving equilibrium as to call forth an equivalent reaction which balances it. If re-equilibration is not thus effected in the individual it is effected in the succession of individuals. Either the species altogether disappears, or else there disappear, generation after generation, those members of it the equilibria of whose functions are least congruous with the changed actions in the environment; and this is the survival of the fittest or natural selection.
If now we persist in thus contemplating the problem as a statico-dynamical one, we shall see that much of the discussion commonly carried on is beside the question. The centre around which the collision of arguments has taken place, is the question of the formation of species. But here we see that this question is a secondary and, in a sense, irrelevant one. We are concerned with the production of evolving and diverging organic forms; and whether these are or are not marked off by so-called specific traits, and whether they will or will not breed together, matters little to the general argument. If two divisions of a species, falling into unlike conditions and becoming re-equilibrated with them, eventually acquire the differences of nature called specific, this is but a collateral result. The essential result is the formation of divergent organic forms. The biologic atmosphere, so to speak, has been vitiated by the conceptions of past naturalists, with whom the identification and classification of species was the be-all and end-all of their science, and who regarded the traits which enabled them to mark off their specimens from one another, as the traits of cardinal importance in Nature. But after ignoring these technical ideas it becomes manifest that the distinctions, morphological or physiological, taken as tests of species, are merely incidental phenomena.
Moreover, on continuing thus to look at the facts, we shall better understand the relation between adaptive and specific characters, and between specific characters and those many small differences which always accompany them. For during re-equilibration there must, beyond those changes of structure required to balance outer actions by inner actions, be numerous minor changes. In any complex moving equilibrium alterations of larger elements inevitably cause alterations of elements immediately dependent on them, and these again of others: the effects reverberate and re-reverberate throughout the entire aggregate of actions down to the most minute. Of resulting structural changes a few will be conspicuous, more will be less conspicuous, and so on continuously multiplying in number and decreasing in amount.
Here seems a fit place for remarking that there are certain processes which do not enter into these re-equilibrations but in a sense interfere with them. One example must suffice. Among dogs may be observed the trick of rolling on some mass having a strong animal smell: commonly a decaying carcase. This trick has probably been derived from the trick of rolling on the body of an animal caught and killed, and so gaining a tempting odour. A male dog which first did this, and left a trail apt to be mistaken for that of prey, would be more easily found by a female, and would be more likely than others to leave posterity. Now such a trick could have no relation to better maintenance of the moving equilibrium, and might very well arise in a dog having no superiority. If it arose in one of the worst it would be eliminated from the species, but if it arose in one of medium constitution, fairly capable of self-preservation, it would tend to produce survival of certain of the less fit rather than the fittest. Probably there are many such minor traits which are in a sense accidental, and are neither adaptive nor specific in the ordinary sense.
§ 174h. But now let it be confessed that though all phenomena of organic evolution must fall within the lines above indicated, there remain many unsolved problems.
Take as an instance the descent of the testes in the Mammalia. Neither direct nor indirect equilibration accounts for this. We cannot consider it an adaptive change, since there seems no way in which the production of sperm-cells, internally carried on in a bird, is made external by adjustment to the changed requirements of mammalian life. Nor can we ascribe it to survival of the fittest; for it is incredible that any mammal was ever advantaged in the struggle for life by this changed position of these organs. Contrariwise, the removal of them from a place of safety to a place of danger, would seem to be negatived by natural selection. Nor can we regard the transposition as a concomitant of re-equilibration; since it can hardly be due to some change in the general physiological balance.
An example of another order is furnished by the mason-wasp. Several instincts, capacities, peculiarities, which are in a sense independent though they cooperate to the same end, are here displayed. There is the instinct to build a cell of grains of sand, and the ability to do this, which though in a sense separate may be regarded as an accompaniment; and there is the secretion of a cement—a physiological process not directly connected with the psychological process. After oviposition there comes into play the instinct to seek, carry home, and pack into the cell, the small caterpillars, spiders, &c., which are to serve as food for the larva; and then there is the instinct to sting each of them at a spot where the injected hypnotic poison keeps the creature insensible though alive till it is wanted. These cannot be regarded as parts of a whole developed in simultaneous coordination. There is no direct connexion between the building instinct and the hypnotizing instinct; still less between these instincts and the associated appliances. What were the early stages they passed through imagination fails to suggest. Their usefulness depends on their combination; and this combination would seem to have been useless until they had all reached something like their present completeness. Nor can we in this case ascribe anything to the influence of teaching by imitation, supposed to explain the doings of social insects; for the mason-wasp is solitary.
Thus the process of organic evolution is far from being fully understood. We can only suppose that as there are devised by human beings many puzzles apparently unanswerable till the answer is given, and many necromantic tricks which seem impossible till the mode of performance is shown; so there are apparently incomprehensible results which are really achieved by natural processes. Or, otherwise, we must conclude that since Life itself proves to be in its ultimate nature inconceivable, there is probably an inconceivable element in its ultimate workings.
END OF VOL. I.