The present chapter is on a priori lines and will perhaps be dismissed with a wave of the hand or hurriedly skimmed over, but I pray the reader at least to read the two or three last pages of it. It is at any rate suggestive, and perhaps I may anticipate the comments of the neo-Darwinian and throw myself on his mercy by mentioning a remark of the late Sir Andrew Clark, prince of physicians and genial cynic, which he made to a patient in my presence. A lady not distinguished for depth of thought asked him a rather silly question in medicine. As if offended he drew himself up, holding in his hand a cup of tea which he was enjoying, and replied at once “Madam, you must get a younger and more inexperienced man than I am to answer you that question.”

A very high degree of probability may be attached to the presupposi­tion that Lamarckian factors, even in their humblest form, may enter into the story of the organisms as historical and living beings. Every hypothesis in matters of science, or, to put it at its lowest, every scientific guess must transcend the evidence at the time available.

Total Experience.

The sugges­tion I venture to make here is that if we take a comprehensive view of certain two great groups of phenomena in nature, which may be termed universal in their extent, it is difficult to conceive that they are not causally connected in the sense that one is the universal antecedent of the other. On the one hand are found universal minute differences, not only between any pair of organisms, but of any two corresponding parts of any organism, even to the size and shape of each leaf on each plant. On the other is universal discontinuity of total experience of all organisms. This term includes all the stimuli of use and environment to which an organism is exposed throughout its whole existence, and its response to them. It includes the whole succession of active and passive stimuli which begin with the formation of a zygote in higher forms, for example, and continue till the death or end of reproductive life of the individual. It stands for such stimuli as arise from habitat on or in the earth, in various levels of salt or fresh water, in sea, lake, pool and river, and in the branches of trees, from climate, from degrees of light, temperature, moisture and wind, from presence and activity of enemies and rivals, from supplies of food, from geographical and topographical position. Such an enumera­tion of stimuli might be much extended if it would serve any purpose. But it is enough to say that the number of such stimuli, and the varying degrees in which these are received and responded to, have hardly any limit which we can conceive. It is a very different and harder task to find out the propor­tion in which such stimuli are advantageous, injurious or indifferent to the organisms, but it may be taken as certain that the vast majority are indifferent in the sense of producing structural change, and, that the advantageous stimuli transmit structural effects to offspring, is only a matter of very strong probability. If the above two groups of phenomena are not causally connected they are intertwined with remarkable closeness and perversity. This aspect of the “web of life” has received attention, and deserves more.

Discontinuous Environments.

Some reference must be made here to observations of Prof. Bateson in his work on variation. In the first place he makes a most valuable statement that “the environment as the directing cause is essential to Lamarck’s theory and as the limiting cause is essential to the doctrine of Natural Selection”36 (which I venture to place in italics on account of its importance to all who seek the pathway of organic evolution) and points out also that “diversity of environment is thus the measure of diversity of specific form. Here then we meet the difficulty that diverse environments often shade into each other insensibly and form a continuous series.”37 This is clearly true and important to the subjects he is discussing. But in regard to the concep­tion with which I am here concerned, that of total experience of organisms, it must be remembered that there is no such thing as an environment apart from the living beings that it environs, and that from this point of view there is no such thing in the world of nature as a continuous environment. The environment of two amoebÆ living under a cover-glass is, for them, far from continuous. In their infinitesimal existence the exact position they occupy in the environing drop of fluid, in which the propor­tion of their humble fare at one side of the cover-glass is not the same as that on the opposite side, renders their environments discontinuous, or different from that of another amoeba occupying a position and “environment” which we should consider identical. And this considera­tion applies to the other few “tropisms” which enter into their little lives. This statement may be difficult to prove, but it is a necessity of thought. An illustra­tion may assist one in visualizing such discontinuity. A fly is seen crawling at its own pace up one of the great pillars of St. Paul’s Cathedral. It comes to one of the thin layers of cement worn down with age and so delicate that a man can just see it in a good light. The fly pauses, and passes into what is for it a chasm, with as much relative delibera­tion as the man would show in passing across a deep railway cutting. The number of pictures that could be made of cases corresponding to that of the amoeba is incalculable. A few will suffice. Two plants of the common nettle are growing on the south side of a ditch in a lane, one rooted a foot higher than the other. The upper one receives throughout its life from wind and sun stimuli slightly different from those received by the lower, and from the soil slightly less moisture. These again receive stimuli very different from another pair on the northern side of the lane. Again in windy weather a clump of sycamores facing the south-west in England, and situated on the ridge of an eminence, will receive very different stimuli from a similar clump on the north-eastern slope of this eminence, and will demonstrate the fact, as to force of wind, by a marked slope to the North East. Even in either of the clumps the individual trees present varying degrees of slope according to their position. The total experience of these two clumps of sycamores and of any two in each clump is obviously different. In a windy situation you can tell in July which is the prevailing wind by noting the main inclina­tion of the ears of corn in a field. Again two male sticklebacks in a pond will make nests for the eggs, there to be deposited, and one will choose a spot on the southern and another on the northern side of a little promontory of soil and stones at the edge of the pond. One will find ready for him materials for building his nest different from those of his rival, and he and his wife and family will receive for that season very different stimuli, and so will the stimuli differ in other phases of their existence in a pond occupying a few square yards. On a sandy bank in a garden facing south you may discover two little caves ingeniously hidden by a small opening, and in each of them you can see a toad. Though these are only a few feet apart one is more widely open to sun and wind than the other and one deeper than the other, and whatever the other activities of the two toads may be in their little shelters, they receive stimuli different in strength and number. On another bank in the same garden less exposed to view, and altogether more sheltered from sun and wind and enemies, a robin has built a well-hidden nest. If the six fledglings in the nest are watched when the mother is absent they are seen to occupy very different positions of comfort, pressure and warmth. When the mother-bird returns from marketing she is hardly impartial in the amount of food she puts into their open beaks. But the slight and perhaps unimportant inequality of their experiences as fledglings is nothing to that which follows when they fly abroad, and which continues to the end of their lives, the life of a robin being somewhere about ten years long. The differences of the total experience of the six young robins is easy to picture. Again, surely, the total experience of two fleas on the body of one plague-rat must be for such small creatures of importance to their welfare, according as their respective “pitches” are on the abdomen, back or legs of the host. When the life-history of a human being is told in full the discontinuity of his total experience needs no proof. The proof is written large before our eyes. But, perhaps, one example may be given. There are two very eminent living writers, whose light has certainly for some years not been hidden under a bushel, Mr. Chesterton and Mr. George Bernard Shaw. We may be said to know them well. Leaving out of sight the Celtic strain claimed by one, and indeed all inherited differences, we see two men of perhaps equal ability, near of an age, both living in London, both living by their pen, both in easy circumstances. When one considers for a moment the different company these two men keep, their different and opposing outlook on life, their different and opposing forms of diet for their minds and bodies (I know which of the two diets of those men I would choose and with which of them I would prefer to be cast on a desert island) one can only say that the total experience of Mr. Chesterton differs from that of Mr. Shaw as cheese from chalk, which things, incidentally, are an allegory in the philosophy of life.

The thought here briefly expressed falls well into line with Prof. Bateson’s statement that the directing cause of the environment is essential to the theory of Lamarck, and I do not hesitate to add to it the assertion that all environment, in the wide sense of total experience, is discontinuous. There are no such phenomena in total experience as unit-characters of allied forms, small variations are the rule. Without doubt a large propor­tion of the stimuli received by an organism are as figures written on a slate and at once wiped off. They are as the snows of yester year. The most they do is to contribute in their measure to the metabolism of the organism, being too numerous and minute to affect any structural change. In a higher form of life none but those which are frequently repeated in the individual and in succeeding generations can effect any structural response.

Mould and Sieve.

It will be remembered that a single example was given of a short-haired dog in which its common habit of lying was associated with a certain pattern of hair. This introduces and illustrates the very wide concep­tion of a moulding process undergone by an organism. It is one familiar to biologists and very much so to Professor Thomson in his various writings. Not less is he an exponent of the metaphorical work of the sieve of natural selection. I therefore claim nothing new when, with the temerity of certain persons treading where others are said to fear to do so, I invent an inclusive term and propose to call the two fundamental factors of organic evolution Plasto-diethesis38 in which the conceptions of mould and sieve are included and hyphenated. This word is no more proposed for its elegance than are panmixia, amphimixis and tetraplasty, though perhaps it may be the etymological superior of one or more of these. It is at any rate inclusive and perhaps sufficiently audacious to assure the inventor of the title of Dr. Pangloss of controversial memory. But as hard words break no bones I have taken this risk and it would appear to be a convenient “conceptual counter” and even Professor Karl Pearson could not consistently forbid it. It has at any rate the merit of having a meaning clear to all friends and opponents alike of Lamarckism. It will be observed that the two words are placed in what I take to be their natural order as expressive of the Alpha and Omega of the story of organic evolution. The moulding process is claimed to precede that of the sieve, as physiology precedes anatomy and function structure, in that form of biological specula­tion which is held here to be the soundest.39

So the banns between Lamarck and Darwin are published, not for the first time of asking, and who shall say that there is cause or just impediment why these two should not be joined together in holy matrimony?

I conclude this chapter with a passage from the life of Columbus by Washington Irving which affords a fitting parallel from history in the higher development and union of two formerly hostile Kingdoms, and the moral of it is clear and simple. But as a forensic junior I beg to enter a caveat to the effect that though the name of Columbus occurs no sugges­tion is made of the discovery of a New World.

“It has been well observed of Ferdinand and Isabella that they lived together not like man and wife whose estates are in common, under the orders of the husband, but like two monarchs strictly allied. They had separate claims to sovereignty in virtue of their separate Kingdoms, and held separate councils. Yet they were so happily united by common views, common interests, and a great deference for each other, that this double administra­tion never prevented a unity of purpose and action. All acts of sovereignty were executed in both their names; all public writings subscribed with both their signatures; their likenesses were stamped together on the public coin, and the royal seal displayed the united arms of Castile and Aragon.”