and here the Lamarckian theory of use and disuse is inapplicable.

A study of the growth of insects shows us that the development of the cuticle scarcely ever takes place without concurrent small variations of the external membranes, especially of the segments, with their brushes of setæ, stings, and so forth. These newly constituted or merely modified membranes, however, are formed or modified before the old protective cuticle is thrown off, and under the protection which it affords. These various membranes must have been formed in a similar manner in the ancestors of the modern insects-that is to say, they were not called into existence by "use or disuse," as the Lamarckian theory maintains; they arose before there could be any question of their use or functional activity, before the protective cuticle had even laid them bare. The newly formed or modified parts could not have any functional activity until they were already formed or modified. Thus the case of the insects proves the direct contrary of what Lamarckism asserts.

Similarly, instructive examples of coadaptation in passive organs to which the Lamarckian theory is inapplicable are adduced by Weismann.1 If reasoning by analogy be permitted in biological science, we might assert that, if numerous cases of coadaptation and correlated variation can be adduced to which the Lamarckian theory of use and disuse is not applicable, and in which coadaptation must result from another cause than that of functional activity, seeing that the coadapted parts are precluded from entering into activity-at least, during the period of their modification; then it is more than probable that the coadaptation of active parts may also be explained without the aid of the Lamarckian theory. That the gradual development of the muscles, for instance, should have accompanied the gradual development of the antlers of the stag, and have been furthered in each individual life by constant use, due to the

1 Weismann, Vorträge über Deszendenztheorie, ii. 70-75.

INSUFFICIENCY OF LAMARCKISM

83

use

increasing strain, is extremely probable, seeing that strengthens an organ. But the variation of the antlers themselves cannot be similarly explained, for the antlers are not active, but passive structures.

Having thus briefly examined the Lamarckian theory as applied to the transmission of mutilations and of instinct, and with reference to the phenomena of coadaptation, we are led to reject it all along the line as an hypothesis which is not merely unproved, but which stands, on the one hand, in contradiction to the facts; and which, on the other, is inapplicable, even were it true, to large categories of cases.

NOTE ON THE HEREDITARY TRANSMISSION OF EPILEPSY.

Since writing the above we have received a communication from Dr. Maurice de Fleury, than whom no one is more competent to express an opinion in regard to the hereditary transmission of epilepsy. Dr. de Fleury entirely confirms us in our scepticism as to the hereditary transmission of this disease. Speaking from personal experience of eighty-seven cases of epilepsy, Dr. de Fleury writes: Never once have I observed that the parents were epileptic. On the contrary, I have always noted that they were not epileptic." Dr. de Fleury states explicitly that the children of epileptic parents are degenerate, and that an accident may cause the general pathological condition of such degenerate offspring to manifest itself as epilepsy. This confirms what we said above. In the same way a syphilitic patient may beget a child with a deformed skull who becomes epileptic. But this has nothing to do with the hereditary transmission of epilepsy itself, which Dr. de Fleury considers to be a non-transmissible disease.

NOTE ON INSTINCT.

It is frequently urged against Weismann's position that the instinct of the hound which causes it to remain motionless when in sight of game -an instinct undoubtedly hereditary-has been acquired under domestication, and has become so greatly strengthened by use in the course of successive generations that it is now inborn in the race. It is to be remarked, in the first instance, that this instinct is very differently developed in different individuals. The sportsman knows well how to distinguish, even in a litter, between the effective pups and the indifferent ones. In the second place, it must be remembered that the hunting instinct of the hound has not by any means been wholly acquired under domestication. This instinct is but a variation of the hunting instinct

which was doubtless inherent in the ancestors of the domesticated hound, as it is inherent in allied species of the canine genus; and which is inherent because it is indispensable to the existence of the species. And just as the original hunting instinct is the result of natural selection, because it is an indispensable adaptation to given conditions of life, so the development of that instinct under domestication is the result of artificial selection, because the breeder treats it as an indispensable quality. The same holds true of the instinct of fidelity in the watch-dog, of docility in the elephant under domestication, etc. These instincts are not entirely novel acquisitions, but are modifications of instincts which were, in their fundamental form, characteristics of the species in question. The improved expression is the necessary outcome of readaptation to changed conditions.

A curious instance of the inefficiency of the Lamarckian theory of use and disuse as primordial factors in evolution is afforded by some poisonous or unpalatable species of butterflies which are invariably slow in their flying movements. We may exclude habit as a cause of this modification of movement, as there is no reason to be found in the external conditions which could have caused these butterflies to fly less quickly than their ancestors. Even if we suppose a few varieties to have been produced whose movements were slow, there is no Lamarckian reason why these varieties alone should have survived; and still less why the movements should become ever slower in the course of succeeding generations. Only when we apply the interpretation afforded by natural selection do we get an explanation of this phenomenon. The varieties which arose with slower movement were more easily recognised by hostile birds than the quickly flying varieties, and were consequently more generally avoided on account of their unpalatable or poisonous qualities. Consequently, these slow-flying varieties survived in greater numbers, multiplied at the expense of their competitors, and bequeathed their instinct for slow movement to their progeny. The slowness of the movement will increase in the course of generations, as long as an increase is advantageous. Once the advantage of a greater sluggishness ceases, variation in that direction ceases also, and the species is adapted to its environment.

CHAPTER V

INSTINCT

MORPHOLOGICAL characters which are of utility to a species in the struggle for existence are due, as to their origin, to natural selection, and are transmissible by heredity. Such characters are, for instance, the colour of animals, and the varied and delicate arrangements for the protection of plants from unwelcome visitors. But psychological as well as morphological characters can be thus selected and transmitted. And we shall see that, unless certain morphological characters, certain animal colours, were invariably associated with corresponding instincts, those morphological characters would be useless to their posThere is thus a necessary correlation between the colour and the instinct of the animal; and even as the first is due to natural selection-we speak now of protective colouring, as distinct from the decorations due to sexual selection—so also is the second.

sessor.

Between reflex action and instinct no strict separation can be established. On the other hand, a voluntary and conscious action can, under certain circumstances, become instinctive.1 Instinct, as Spencer has defined it, is a complex series of reflex actions; and, indeed, when we consider the extraordinary precision of the instincts in many of the lower animals, we are apt to consider them from the human point of view, and to attribute to their possessors psychical faculties analogous to those of man.

1 Vide in Chapter IV. the example of the walrus in the South Sea Islands.

This anthropomorphism, though deeply rooted in the human mind, is none the less deceptive and erroneous. Consciousness is a phenomenon which implies a certain development of the nervous system; and the view which holds the centralisation of the nervous system in certain centres of the brain cortex to be the indispensable condition for the development of consciousness is certainly the correct one. Max Verworn has shown that all stimulated movements in the lower organisms and plants must be regarded as reflex, and that conscious and voluntary action commences only subsequently to the development of the specific nerve centres.1

For this reason we are unable to agree with Ribot, who writes: "Cet état initial (de l'instinct) doit être accompagné de conscience, n'est possible que par elle : il est au sens strict, d'une nature psychique. Considérons maintenant les instincts dans leur dernier terme dans les actes, les résultats auxquels ils aboutissent. Ici encore, il est difficile de ne pas admettre un état de conscience, surtout dans les cas où l'activité de l'animal doit parcourir plusieurs phases dont chacune n'est qu'une étape vers le résultat final."2 Ribot goes on to say that the intermediary phenomena between the initial and the final act, which constitute instinct properly so called, are indeed unconscious; for, as the nervous process is the only indispensable factor in the conscious state, it matters little if consciousness itself disappears in the course of time, provided that the nervous process which constitutes the physiological equivalent of consciousness remain.

Ribot's view is that instinct is nothing but inherited habit; and although this may be true in a certain sense when applied to those instincts which have their origin in an act of conscious volition, Weismann has shown conclusively that it cannot be

1 M. Verworn, Psychophysiologische Protisten-Studien, pp. 135-140. 2 Th. Ribot, L'Hérédité psychologique, 7th edition, p. 18. Paris, Alcan,