We see, further, that the process of the development of all germs that are marked out for independent existence causes a powerful reaction, even from the very beginning of that existence, on both the conscious and unconscious life of the whole organism. We may see this from the fact that the organ of reproduction stands in closer and more important relation to the remaining parts, and especially to the nervous system, than do the other organs; and, inversely, that both the perceived and unperceived events affecting the whole organism find a more marked response in the reproductive system than elsewhere.
We can now see with sufficient plainness in what the material connection is established between the acquired peculiarities of an organism, and the proclivity on the part of the germ in virtue of which it develops the special characteristics of its parent.
The microscope teaches us that no difference can be perceived between one germ and another; it cannot, however, be objected on this account that the determining cause of its ulterior development must be something immaterial, rather than the specific kind of its material constitution.
The curves and surfaces which the mathematician conceives, or finds conceivable, are more varied and infinite than the forms of animal life. Let us suppose an infinitely small segment to be taken from every possible curve; each one of these will appear as like every other as one germ is to another, yet the whole of every curve lies dormant, as it were, in each of them, and if the mathematician chooses to develop it, it will take the path indicated by the elements of each segment.
It is an error, therefore, to suppose that such fine distinctions as physiology must assume lie beyond the limits of what is conceivable by the human mind. An infinitely small change of position on the part of a point, or in the relations of the parts of a segment of a curve to one another, suffices to alter the law of its whole path, and so in like manner an infinitely small influence exercised by the parent organism on the molecular disposition of the germ [78] may suffice to produce a determining effect upon its whole farther development.
What is the descent of special peculiarities but a reproduction on the part of organised matter of processes in which it once took part as a germ in the germ-containing organs of its parent, and of which it seems still to retain a recollection that reappears when time and the occasion serve, inasmuch as it responds to the same or like stimuli in a like way to that in which the parent organism responded, of which it was once part, and in the events of whose history it was itself also an accomplice? [79] When an action through long habit or continual practice has become so much a second nature to any organisation that its effects will penetrate, though ever so faintly, into the germ that lies within it, and when this last comes to find itself in a new sphere, to extend itself, and develop into a new creature—(the individual parts of which are still always the creature itself and flesh of its flesh, so that what is reproduced is the same being as that in company with which the germ once lived, and of which it was once actually a part)—all this is as wonderful as when a grey-haired man remembers the events of his own childhood; but it is not more so. Whether we say that the same organised substance is again reproducing its past experience, or whether we prefer to hold that an offshoot or part of the original substance has waxed and developed itself since separation from the parent stock, it is plain that this will constitute a difference of degree, not kind.
When we reflect upon the fact that unimportant acquired characteristics can be reproduced in offspring, we are apt to forget that offspring is only a full-sized reproduction of the parent—a reproduction, moreover, that goes as far as possible into detail. We are so accustomed to consider family resemblance a matter of course, that we are sometimes surprised when a child is in some respect unlike its parent; surely, however, the infinite number of points in respect of which parents and children resemble one another is a more reasonable ground for our surprise.
But if the substance of the germ can reproduce characteristics acquired by the parent during its single life, how much more will it not be able to reproduce those that were congenital to the parent, and which have happened through countless generations to the organised matter of which the germ of to-day is a fragment? We cannot wonder that action already taken on innumerable past occasions by organised matter is more deeply impressed upon the recollection of the germ to which it gives rise than action taken once only during a single lifetime. [80a]
We must bear in mind that every organised being now in existence represents the last link of an inconceivably long series of organisms, which come down in a direct line of descent, and of which each has inherited a part of the acquired characteristics of its predecessor. Everything, furthermore, points in the direction of our believing that at the beginning of this chain there existed an organism of the very simplest kind, something, in fact, like those which we call organised germs. The chain of living beings thus appears to be the magnificent achievement of the reproductive power of the original organic structure from which they have all descended. As this subdivided itself and transmitted its characteristics [80b] to its descendants, these acquired new ones, and in their turn transmitted them—all new germs transmitting the chief part of what had happened to their predecessors, while the remaining part lapsed out of their memory, circumstances not stimulating it to reproduce itself.
An organised being, therefore, stands before us a product of the unconscious memory of organised matter, which, ever increasing and ever dividing itself, ever assimilating new matter and returning it in changed shape to the inorganic world, ever receiving some new thing into its memory, and transmitting its acquisitions by the way of reproduction, grows continually richer and richer the longer it lives.