Science and Morals and Other Essays, Sir Windle Bertram Coghill Alan [reading books for 7 year olds .TXT] 📗

the possibility that the peculiarity may have been also possessed by some other member of the family. But on the whole the offspring does closely resemble its parents; that is to say, not only the species and the variety but the individual "breeds true." "Look like dey are bleedzed to take atter der pa," as Uncle Remus said when he was explaining how the rabbit comes to have a bobtail. Moreover this resemblance is not merely in the great general features. Apart from monstrosities, the children of human beings are human beings; the children of white parents have white skins, those of black progenitors are black. Commonly, though not always by any means, the children of dark-haired parents are themselves dark-haired, and so on. But smaller features are also transmitted, and transmitted too for many generations; for example, the well-known case of the Hapsburg lip, visible in so many portraits of Spanish monarchs and their near relatives, and visible in life to-day. Again, there are families in which the inner part of one eyebrow has the hairs growing upwards instead of in the ordinary way, a feature which is handed on from one generation to another. Even more minute features than this have been known to be transmissible and transmitted, such as a tiny pit in the skin on the ear or on the face. In fact, there is hardly any feature, no matter how small, which may not become a hereditary possession.

If in-and-in breeding occur, as it may do amongst human beings in a locality much removed from other places of habitation, it may even happen that what may be looked upon as a variety of the human race may arise, though when it arises it is always easy to wipe it out and restore things to the normal by the introduction of fresh blood, to use the misleading term commonly employed, where the Biblical word "seed" comes much nearer to the facts.

Thus there is a well-authenticated case in France (in Brittany if I remember right) of a six-fingered race which existed for a number of generations in a very isolated place and was restored to five-fingeredness when an increase in the populousness of the district permitted a wider selection in the matter of marriages.

And similarly, not long ago an account was published of an albino race somewhere in Canada which had acquired a special name.

Perhaps it has been wiped out by this time by wider marriages, though these might be effected with greater difficulty by albinos than by six-fingered persons. At any rate no one can doubt that it might at any time be wiped out by such marriages, though even when apparently wiped out, sporadic cases might be expected to occur: what the breeders call "throws-back," when they see an animal which resembles some ancestor further back in the line of descent than its actual progenitors. Certainly the most remarkable instance of the reliance which we have come to feel respecting this matter of inheritance is that which was afforded by a recent case of disputed paternity interesting on both sides of the Atlantic, since the events in dispute occurred in America and the property and the dispute concerning it were in England.

It was obviously a most difficult and disputable case, but the judge, a shrewd observer, noticed, when the putative father was in the box, a feature in his countenance which seemed closely to resemble what was to be seen in the child which he claimed to be his own. A careful examination of the parents and of the child was made by an eminent sculptor, accustomed to minute observation of small features of variety in those sitting to him as models.

He reported and showed to the court that there were remarkable features in the head of the child which resembled, on the one hand an unusual configuration in the mother—or the woman who claimed to be the mother—and on the other a well-marked feature in her husband. And as a result the father and mother won their case, and were proclaimed the parents of the child because of the resemblance of these features; and, if we think for a moment, we shall see, because also of the reliance which the human race has come to place in the fidelity of inheritance, of its perfect certainty, so to speak, that a duck will not come out of a hen's egg, and the fact of this reliance on a generally received truth remains, whatever may be said as to the legal aspect of such evidence.

Inheritance is a fact recognised by everybody, and the only reason why we refuse to wonder at it is because, like other wonderful yet everyday facts, such as the growth of a great tree from a tiny seed, it is so everyday that we have ceased to wonder at it. It is there: we know that. But have we any kind of idea how it comes about? The duck does not, as a matter of common experience, come out of a hen's egg. Why does it come out of a duck's egg? Why doesn't it come out, if only rarely, from a hen's egg? In other words, do we know what it is that explains inheritance or how it is that there is such a thing as inheritance? Well, candour obliges me to say that we do not. In spite of all the work which has been expended upon this question we are totally ignorant of the mechanism of heredity. Nevertheless it will be instructive to glance at the theories which have been put forward to explain this matter.

All living things spring from a small germ, and in the vast majority of cases this germ is the product in part of the male and in part of the female parent. It is therefore natural that we should in the first place turn our attention to this germ and ask ourselves whether there is anything in its construction which will give us the key of the mystery. There is not, at least there is nothing definite as shown by our most powerful microscopes. To be sure there is a remarkable substance, called chromatin because of its capacity for taking up certain dyes, which evidently plays some profoundly important part in the processes of development. We may suspect that this is the thing which carries the physical characteristics from one generation to another, but we cannot prove it; and though some authorities think that it is, others deny it. Even if it be, it can hardly be supposed that microscopic research will ever be able to establish the fact, and that for reasons which must now be explained.

Let us suppose that we visit a vast botanic garden, and in the seed-time of each of the plants therein contained select from each plant a single ripe seed. It is clear that, if we take home that collection of seeds, we shall have in them a miniature picture of the garden from which they were culled, or at least we shall be in possession of the potentiality of such a garden, for, if we sow these seeds and have the good fortune to see them all develop, take root and grow, we shall actually possess a replica of the garden from which they came. Not exactly, it may be urged, for the distribution or arrangement of the seeds must have been carefully looked to, if the gardens are to resemble each other otherwise than in the mere possession of identical plants. I admit the truth of this, but cannot for the moment discuss it. At any rate we should have the same plants in both gardens.

On this analogy, many have suggested that every organ in the body—we must go further, and say that every marked feature in every organ in the body—is represented in the germ by a seed which can grow, under favourable circumstances, into just such another organ or feature of an organ. This was the theory put forward by Darwin under the name of "pangenesis," and by others under other titles with which it is unnecessary to burden these pages. All these theories have been summed together under the name "micromeristic," that is small-fragmented, or again, "particulate," since they all postulate the existence in the germ of innumerable small fragments—seeds—which are capable of growing into complete plants or organs under favourable circumstances. Again, this, even if true, does not by any means exhaust the matter, for it does not explain why the seed of the eye implants itself and grows in the right place in the head instead of making a home for itself, let us say, in the sole of the foot. But again we must pass over that matter.

There is nothing inherently impossible in this theory; indeed, if we allow that the transmission of inheritable characteristics is purely material, and it may be, there is only one other conceivable way in which it can occur. It is true that the seeds must be almost innumerable, but the germ, though small, is capable of accommodating an almost innumerable number of independent factors, if the prevalent views as to the constitution of matter are to be believed. And, as it is quite inconceivable that we can ever have microscopes which could detect such minute objects as the ultimate bricks of which the atom—no, not even the atoms themselves which compose the germ—consists, it is impossible that we should be able to say that the seed-theory is untrue. Even if we could see these ultimate constituents it is in the last degree unlikely that they would have any resemblance to the things which are, on this theory to grow from them, any more than the acorn resembles the oak which is to spring from it.

But observe! the germ on this view must contain not only seeds from the immediate parents but from many, perhaps all, of the older generations of the family, otherwise how are we to account for the appearance of ancestral peculiarities which the father and mother do not show? Moreover, since very minute things, like the inner angle of the eyebrow, may independently vary, there must be an enormous number of seeds apart altogether from the considerations alluded to in the last paragraph. And many authorities who have closely considered the question have come to the conclusion that the complexities introduced would be so great that it is impossible to believe in any micromeristic theory.

Then, of course, we must look out for some other explanation, and some have suggested that it is to be found in memory—the memory of the germ of what it was once part and the anticipation of what it may once more be. This again is an explanation not susceptible of proof along the lines of a chemical experiment, but not necessarily, therefore, untrue. Of course there are two ideas as to memory. If we are pure materialists and imagine every memory in our possession as something stamped, in some wholly incomprehensible manner, on some cell of our brain and looked at there, by some wholly inconceivable agency, when we sit down to think of past days, then we must look on the germ, under the "mnemic" or memory theory as consisting of fragments each of them impressed with the "memory" of some particular organ or feature of the body, and lo! we find ourselves back again in micromerism. If we are to take a non-materialistic view of memory we are plunged into a metaphysical discussion which cannot here be pursued. A third explanation, which by the way explains nothing, is that the whole matter is one of "arrangement," to which we shall return at the close of this paper.

The mechanism of inheritance must either be physical[33] or it must be