Is

the whole group eventually becomes extinct. Prof. Marcus Hartog argues from this and similar researches made by other enquirers that conjugation or fertilisation plays an important part in warding off senescence. such introduction of fresh blood necessary to ward off senescence and prevent germinal impairment in the case of higher animals, human beings in particular? With regard to certain domestic animals, there is reason to think that close in-breeding is followed by a gradual deterioration of offspring; and experienced breeders are practically unanimous that the effect of this is to produce debility, abnormalities, and eventually sterility. As Sir Francis Darwin says, it is generally admitted that degeneration either in constitution or in other ways does ultimately ensue; so that at any cost the breeder is absolutely compelled to admit blood from another family or strain of the same race.' In the case of human beings, however, in-and-in breeding to this extent is practically unknown; and it is therefore unlikely that senescence of the germ-plasm from such a cause plays any practical part in the production of degeneracy. At the same time it is to be remarked that the effect of consanguineous marriages is to intensify any existing defect; and the same is true where mating is rigidly restricted to the members of any one small section of society. We are apt nowadays to bewail the not infrequent union of members of our old and formerly exclusive aristocracy with chorus girls and the like. The process may be attended with a serious decline in 'form' and manners; but it is possible that it may possess physiological compensations which are beneficial to the race as a whole.

We have now to consider the question of the modification of the germ-plasm by the environment. Fifty years ago few scientific persons would have doubted this; and even to-day it is probable that most medical men would say that their clinical experience supported such a view. But in those days it was supposed that the germ-cells arose, by some means or other, from the body-cells; it followed that their condition was dependent upon the condition of the body-cells, and the production of germvariations through the environment was a necessary and logical sequence. But recent writers, particularly

Professor Weismann, have proclaimed the 'continuity'
of the germ-plasm; they have contended, in other words,
that it is not produced anew in each individual, but is an
independent plasm which is handed on from generation
to generation as a separate entity; and it is consequently
argued that the germ-plasm is immune to its surround-
ings. Some writers have even gone so far as to say not
only that the environment has, in fact, no influence in
the production of germ-variations, but that it cannot
have any such influence, because, if it had, it would be
subversive of the whole doctrine of evolution. Since
this argument strikes at the very root of what I conceive
to be the origin of degeneracy, it will be well to consider
the basis upon which the assertion is made. And in this
connexion I cannot do better than quote the words of
Dr Archdall Reid, who is perhaps the most strenuous
advocate of this view.
Dr Reid says:

'If this theory that germinal changes may be caused by
waste products, circulating toxins and the like, is correct, all
races affected by any sort of disease should drift steadily
towards extinction.' Again: 'If disease produces any
germinal change, then, no matter how small and imperceptible
the differences between one generation and the next, . . . the
constant accentuation of the alteration during hundreds,
perhaps thousands, of generations must make it at last mani-
fest and unmistakable.' . . . The facts are decisive; nearly
all human races have been exposed to disease for thousands
of years, and in no instance is there to be found an iota of
evidence that any race has, as a consequence, become degene-
rate' (pp. 260-262).

Now, at first sight these statements may appear very plausible; but a little reflexion will show them to be really fallacious in that they entirely disregard one important consideration, namely, the possibility that the vulnerability of the germ-plasm may vary greatly in different individuals. In the case of the ordinary tissues and organs of the body-the somatoplasm-there is no doubt whatever on this point; and one of the bestestablished facts in medicine is that of the varying resistance to disease presented by different individuals. Thus, one person will rapidly succumb to Tuberculosis, Influenza, Pneumonia or other toxic process; another will escape

death but evince considerable subsequent deterioration; while a third will recover without any permanent ill effects. It is surely not unjustifiable to consider that similar differences of vulnerability may exist in the case of the germ-plasm. Adverse factors of the environment will then not be operative upon the germ-plasm of the whole community, but only upon that of the susceptible portion; and it will no more follow that 'all races affected by any sort of disease should drift steadily towards extinction' than it follows that all persons affected with Tuberculosis, Influenza, or other disease will necessarily die of those complaints. Further, not only may some germ-plasm be practically immune, but plasm which is susceptible may be influenced to varying extent, both quantitatively and qualitatively, thereby giving rise to many different forms of variation and degrees of degeneracy.

As a matter of fact this is precisely what happens; and the manifestations of degeneracy as seen in daily life vary within very wide limits. In some instances the variation is so pronounced as to interfere seriously with the survival value of the resulting offspring. Such individuals will then be eliminated by natural selection, provided this is sufficiently rigorous, so that, far from being subversive of the doctrine of evolution, the process is one which actually conduces to racial evolution. It may happen, however, that the variation is much less pronounced and the social environment not sufficiently rigorous to bring about elimination. Such individuals will then not only be enabled to survive, but will intermarry with those whose germ-plasm is unimpaired, with the result that a dilution of the morbid process may take place so far as individual members are concerned, but there will be a more widespread dissemination throughout the community.

As will presently be shown, these milder manifestations of degeneracy occur more particularly in the central nervous system. They involve those parts of the nervous system concerned with the higher processes of mind, and they take the form of a diminished mental potentiality, a lessened vigour and initiative, a want of balance and a loss of control. The social expression of these changes is seen in an incapacity of the community

for sound government and legislation, for organisation and for social progress, and an inability to compete with more vigorous neighbours, both in the arts of peace and in those of war, the natural termination of which is social decline or even disruption. It is exceedingly questionable if any student of history will be found to maintain that there is not an iota of evidence' of the past existence of such degeneracy.

As to why the germ-plasm of different individuals should vary in susceptibility to the action of adverse factors of the environment, we know very little. It is not inconceivable, indeed it is a reasonable assumption, that its state of nutrition may be subject to change, and that this may determine its immunity or vulnerability; or the same result may be brought about by the absence or deficiency of some internal secretion. This question is one of great moment, but it is too intricate to enter upon in this place.

The fact is, then, that not only are there no a priori reasons against the modification of the germ-plasm by the environment, in spite of much reiteration to the contrary, but there are many such reasons in favour of this modification taking place. Doubtless the germmaterial possesses a considerable degree of resistance to the action of the environment; for, were it otherwise, and did it reflect every transient change, racial stability could hardly exist. But there is a great difference between some degree of resistance and absolute immunity; and, when we remember that after all the germ-plasm is still living protoplasm and consequently dependent for its sustenance upon the quantity and quality of the fluids supplied to it, the view that it can lead a charmed life, utterly uninfluenced by any condition of its host, is untenable. As Beard says, the germ-cell must react to and be influenced by its environment-a conclusion not only accepted by most competent biologists of the present day, but acquiesced in by Weismann himself.

However, the question is no longer one of speculation and a priori reasoning. Whatever may be asserted of the theoretical impossibility that the germ-cell should be adversely affected by its environment, there is now very clear evidence that it is so affected; and to some

of this evidence we may briefly refer. One of the earliest observations (1861) was that of Dr Constantin Paul regarding the effect of lead. This observer found that out of thirty-two pregnancies, in which the father alone suffered from lead poisoning, the mother being free from that condition, twelve of the children were stillborn, eight died during the first, four during the second, and five during the third year of life, while another died later in childhood. Similar data were published by Lizé (1862) regarding workers exposed to the fumes of nitrate of mercury. Out of twelve pregnancies in which the father alone was exposed, there were four stillbirths; of the remaining eight children, three died before the fourth year, and only one of those who survived could be described as vigorous. The toxic effects of alcohol upon growing protoplasm are well known; and, since experimentation with this is comparatively easy, it has naturally formed the subject of many investigations. One of the most recent is that by Stockard upon guinea-pigs, by which it was shown that the net result of twenty-four matings of alcoholised fathers with normal mothers was only five surviving offspring, or no more than might have been expected from a single pairing of two healthy animals; and, further, that at the age of two months these five survivors were only half the usual size. Dr E. Bertholet, after a series of microscopical examinations in 120 alcoholic and non-alcoholic human beings, was able to demonstrate very clear differences, and to assert that 'the hurtful influence of chronic alcoholism upon sexual glands is not to be denied.' Similar results have been obtained with other poisons; and during recent years it has also been shown that germ variations may be induced by temperature (Sumner, Bordage, Tower) and by the injection of chemicals into the immature ovary (Macdougal). Finally, from enquiries which I have lately made into the effect of X-rays, there seems to be no doubt that males working with unprotected tubes are rendered temporarily sterile owing to the action of the rays upon the sperm-cells. If this and other agencies can thus bring about the death of the germ-cell, it is a justifiable inference that smaller doses can so injure it as to produce a living but impaired offspring; and the