consequent disuse, and the transmission (as Lamarck would have supposed) of a more and more weakened and structurally impaired eye to the offspring in successive generations, until the eye finally disappeared. But this instance is really fully explained (as the present writer has shown) by the theory of natural selection acting on congenital fortuitous variations. It is definitely ascertained that many animals are thus born with distorted or defective eyes whose parents have not had their eyes submitted to any peculiar conditions. Supposing a number of some species of arthropod or fish to be swept into a cavern or to be carried from less to greater depths in the sea, those individuals with perfect eyes would follow the glimmer of light and eventually escape to the outer air or the shallower depths, leaving behind those with imperfect eyes to breed in the dark place. A natural selection would thus be effected. In every succeeding generation this would be the case, and even those with weak but still seeing eyes would in the course of time escape, until only a pure race of eyeless or blind animals would be left in the cavern or deep sea.
It is a remarkable fact that it was overlooked alike by the supporters and opponents of Lamarck’s views until pointed out by the present writer (Nature, 1894, p. 127), that the two statements called by Lamarck his first and second laws are contradictory one of the other. Lamarck’s first law asserts that a past history of indefinite duration is powerless to create Educability. a bias by which the present can be controlled. He declares that in spite of long-established conditions and correspondingly evoked characters new conditions will cause new responsive characters. Yet in the second law he asserts that these new characters will resist the action of yet newer conditions or a reversion to the old conditions and be maintained by heredity. If the earlier characters were not maintained by heredity why should the later be? If a character of much longer standing (certain properties of height, length, breadth, colour, &c.) had not become fixed and congenital after many thousands of successive generations of individuals had developed it in response to environment, but gave place to a new character when new moulding conditions operated on an individual (Lamarck’s first law), why should we suppose that the new character is likely to become fixed and transmitted by mere heredity after a much shorter time of existence in response to environmental stimulus? Why should we assume that it will be able to escape the moulding by environment (once its evoking cause is removed) to which, according to Lamarck’s first law, all parts of organisms are subject? Clearly Lamarck gives us no reason for any such assumption, and his followers or latter-day adherents have not attempted to do so. His enunciation of his theory is itself destructive of that theory. Though an acquired or “superimposed” character is not transmitted to offspring as the consequence of the action of the external agencies which determine the “acquirement,” yet the tendency to react to such agencies possessed by the parent is transmitted and may be increased and largely developed by survival, if the character developed by the reaction is valuable. This newly discovered inheritance of “variation in the tendency to react” has a wide application and has led the present writer to coin the word “educability.” It has application to all kinds of organs and qualities, but is of especial significance in regard to the development of the brain and the mental qualities of animals and of man (see the jubilee volume of the Soc. de Biologie, 1899, and Nature, 1900, p. 624).
It has been argued that the elaborate structural adaptations
of the nervous system which are the corporeal correlatives of
complicated instincts must have been slowly built
up by the transmission to offspring of acquiredTheory
of trans-
mission of instincts.
experience, that is to say, of acquired brain structure.
At first sight it appears difficult to understand how
the complicated series of actions which are definitely
exhibited as so-called “instincts” by a variety of animals can
have been due to the selection of congenital variations, or can
be otherwise explained than by the transmission of habits
acquired by the parent as the result of experience, and
continuously elaborated and added to in successive generations.
It is, however, to be noted, in the first place, that the imitation
of the parent by the young possibly accounts for some part of
these complicated actions, and, secondly, that there are cases
in which curiously elaborate actions are performed by animals
as a characteristic of the species, and as subserving the general
advantage of the race or species, which, nevertheless, can not
be explained as resulting from the transmission of acquired
experience, and must be supposed to be due to the natural
selection of a fortuitously developed habit which, like fortuitous
colour or form variation, happens to prove beneficial. Such
cases are the habits of “shamming dead” and the combined
posturing and colour peculiarities of certain caterpillars
(Lepidopterous larvae) which cause them to resemble dead twigs or
similar surrounding objects. The advantage to the animal of
this imitation of surrounding objects is that it escapes the
pursuit of (say) a bird which would, were it not deceived by the
resemblance, attack and eat the caterpillar. Now it is clear
that preceding generations of caterpillars cannot have acquired
this habit of posturing by experience. Either the caterpillar
postures and escapes, or it does not posture and is eaten; it is
not half eaten and allowed to profit by experience. We seem
to be justified in assuming that there are many movements of
stretching and posturing possible to caterpillars, and that some
caterpillars had a congenital fortuitous tendency to one position,
some to another, and, finally that among all the variety of
habitual movements thus exhibited one has been selected and
perpetuated because it coincided with the necessary conditions
of safety, since it happened to give the caterpillar an increased
resemblance to a twig.
The view that instinct is the hereditarily fixed result of habit derived from experience long dominated all inquiry into the subject, but we may now expect to see a renewed and careful study of animal instincts carried out with the view of testing the applicability to each instance of the pure Darwinian theory without the aid of Lamarckism.
Nothing can be further from the truth than the once favourite theory that instincts are the survivals of lapsed reasoning processes. Instincts, or the inherited structural mechanisms of the nervous centres, are in antagonism to the results of the reasoning process, which are not capable of hereditary transmission. Every higher vertebrate animal possesses the power of forming for itself a series of cerebral mechanisms or reasoned conclusions based on its individual experience, in proportion as it has a large cerebrum and has got rid of or has acquired the power of controlling its inherited instincts. Man, The Record of the Past. compared with other animals, has the fewest inherited mental mechanisms or instincts and at the same time the largest cerebrum in proportion to the size of his body. He builds up, from birth onwards, his own mental mechanisms, and forms more of them, that is to say, is more “educable,” and takes longer in doing so, that is to say, in growing up and maturing his experience, than any other animal. The later stages of evolution leading from his ape-like ancestors to man have consisted definitely in the acquirement of a larger and therefore more educable brain by man and in the consequent education of that brain. A new and most important feature in organic development makes its appearance when we set out the facts of man’s evolutional history. It amounts to a new and unprecedented factor in organic development, external to the organism and yet produced by the activity of the organism upon which it permanently reacts. This factor is the Record of the Past, which grows and develops by laws other than those affecting the perishable bodies of successive generations of mankind, and exerts an incomparable influence upon the educable brain, so that man, by the interaction of the Record and his educability, is removed to a large extent from the status of the organic world and placed in a new and unique position, subject to new laws and new methods of development unlike those by which the rest of the living world is governed. That which we term the Record of the Past comprises the “taboos,”
