that type of degeneracy which appears in spite of a satisfactory environment. The defect here is clearly germinal; it is, in fact, a germ-variation, and as such is transmissible to subsequent generations in accordance with the laws of heredity.

In view of this important and far-reaching difference between these two types, usually comprehended by the word degeneracy,' some verbal distinction is clearly necessary. In my opinion that term should be restricted to the latter group, accordingly I venture to define degeneracy as 'a retrograde condition of the individual resulting from a pathological variation of the germcell'; and it is in this sense that it will here be used. Perhaps the most convenient word to denote the somatic modification arising from a defective environment would be 'decadency.'

Degeneracy, then, is the expression of a germvariation. It is generally accepted by biologists that variations of the germ-cell tend to be transmitted to subsequent generations. It is doubtful whether this transmission is invariable, and the laws governing it are still very imperfectly known, but, as a broad fact, it is certainly true. It follows that the occurrence of variations is a phenomenon of the utmost importance to the future of the race. Such variations may be divided into two main groups. Firstly, those which connote an increased potentiality for development in some particular direction, thereby placing the individual at a greater advantage in the struggle for existence. These may be termed 'progressive' variations, and they obviously lie at the root of progressive racial evolution. Secondly, those which connote a diminished potentiality for development of such a nature as to impair the survival value. These may be termed 'retrogressive' variations and lie at the root of social degeneracy. It is with this latter class only that we are now concerned.

The prevention of the perpetuation of these retrogressive variations is clearly a social problem of great moment, and comprises what is known as restrictive or negative eugenics. But the problem of their causation is even more important; for restrictive eugenics, however complete, can never prove entirely satisfactory so Vol. 228.-No. 452.

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long as degenerates are still being produced de novo. Accordingly it is chiefly with the question of causation that it is proposed to deal.

There are three chief views as to this causation, which may be discussed seriatim. The first is, that degeneracy is not the expression of any new germinal change, but the perpetuation of a defect which has existed in certain strains or stocks of the human race from the very beginning or from a Simian ancestry. This idea has probably occurred to most thinkers on the subject, but it has recently again been advanced by Dr C. B. Davenport of America. Dr Davenport,* speaking of the origin of mental defect, says:

'The conclusion is forced upon us that the defects of this germ plasm have surely come all the way down from man's ape-like ancestors, through two hundred generations or more. The germ plasm that we are tracing remains relatively simple; it has never gained, or only temporarily, at most, the one or the many characteristics whose absence we call (quite inadequately) "defects." Feeble-mindedness is thus an uninterrupted transmission from our animal ancestry. It is not reversion; it is direct inheritance.'

Now, with regard to this theory, we must either assume that the defect has been present since the very origin of life, or, that it has appeared at some subsequent period. On the former view it is presumed that the innate potentiality only sufficed for the attainment of a certain low stage of mental development; degeneracy, however, is no mere evolutionary arrest at some particular phase; it is usually seen as, if I may venture to use such a term, a progressive retrogression of certain stocks. If, however, we admit that the variation has made its appearance at some later stage of evolution, then this theory affords no explanation as to its causation; it simply pushes the enquiry back to that period, 'two hundred generations or more.'

In this connexion it may be remarked that atavism is not uncommonly invoked as the explanation of feeblemindedness, which is one of the most prevalent forms of

The origin and control of mental defectiveness,' 1912.

degeneracy. It is contended that, for some reason or other, these persons reproduce, or hark back to, a stage of mental development which was typical of savage or prehistoric man, but from which normal mankind have evolved. It is inferentially suggested that, although mental defectives are incapable of holding their own in a civilised community, they would not be incapable of so doing among these more primitive types. I cannot accept this view. I find it exceedingly difficult to believe that the feeble-minded members of a civilised community would be any better able to hold their own among a community of savages than they are in their present environment; and I find it still more difficult to imagine that such persons represent a normal developmental phase in the mental evolution of the human race.

In this place also reference may be made to a recent work by V. A. Moschkoff ('Neue Theorie von der Abstammung des Menschen und seiner Degeneration'). This author looks upon the whole of mankind as being blended in various degrees from two types-white diluvial man and Pithecanthropus. He describes the physical, mental and moral characteristics of these types with a minuteness which puts the deductive ability of Owen completely in the shade, and which might, indeed, almost be the outcome of a personal acquaintance with these primeval beings in the flesh. White diluvial man would appear to have been a sort of Apollo, the possessor of many beauties and virtues, and of a body which was in every way more perfect than any now existing. Pithecanthropus, on the other hand, was a speechless, repulsive being, apparently somewhat midway between an African pygmy and a modern gorilla. According to Moschkoff, not only is degeneracy, as seen in idiots, cretins, and certain ethnic groups, due to a reversion to the pithecanthropic element, but the alternate expression of the characters of these two stocks takes place at different ages in the same individual and at different cycles in the life of the nation, and so leads to successive alterations of individual character, and even to progressive and retrogressive changes involving the whole community. Even civil wars and internal dissensions, which the sociologist usually attributes to economic causes, are claimed by the author as being due to the

swing of the pendulum bringing into play a preponderating pithecanthropic element. And the pendulum would appear to swing so regularly, that, given the requisite biological data, he would even be able to forecast which would be the fat and which the lean years of a nation's future. Can anything more be expected of science than this?

The second theory of causation is that these retrogressive variations are not caused, but arise of themselves; in other words, that they are 'spontaneous' in origin. Thus, in the Report of the Royal Commission on the Feeble-minded the following statement occurs: Both on the ground of fact and of theory there is the highest degree of probability that feeble-mindedness is usually spontaneous in origin, that is, not due to influences acting on the parent.' Now, as Huxley remarked many years ago, to say that a variation is spontaneous is simply to express our ignorance of its causation; and it is obvious that this theory of 'spontaneous variation' is extremely unsatisfactory. The more we learn of the phenomena of nature, the more do we find evidence of law and order; and it would be strange, to say the least, if chance and not law should control what is probably the most important happening in the whole of nature.

The third view is that retrogressive germ-variations have neither existed ab initio nor are spontaneous in origin, but are produced by the operation of natural processes and in obedience to natural laws. In my opinion this is not only the most reasonable view in itself, but the only one which is supported by definite evidence; and, although it is not yet possible fully to explain the manner of production of these germ-variations, it is possible to advance certain considerations which at least possess the merit of carrying us a step further towards the elucidation of this problem.

If we pass for a moment from the germ-cells to consider the cells of the body, we find that retrogressive changes occur under two conditions: firstly, in consequence of an endogenous decline of their vitality; secondly, through the action of external agencies. The former of these changes occurs in old age. By this is not meant old age as expressed by years; some persons are old at forty, others still young at eighty. What is

meant is that condition of senescence which results from the exhaustion of the inherent vitality of the cells. They are unable to function because they have come to the end of their physiological banking account. Decay arising from without is best exemplified by the action of such inorganic and organic poisons as alcohol, lead, and phosphorus, or by toxic bodies produced by certain microorganisms. These agents may bring about such a deterioration of important cells and tissues that the death of the individual results. The problem we have to consider is whether the germ-cells may be affected by similar agencies. May they undergo pathological variation in consequence of senescence? May the same result be caused by adverse factors of the environment?

To begin with the first of these questions-as the modern conception of the continuity of the germ-plasm has become popular, it is not infrequently said that this plasm is immortal.' But, even if it be granted that germ-plasm existing to-day is the lineal descendant of plasm which has existed since the origin of life, this statement requires some qualification. The unexpended germ-cells not only die, of course, at the death of the individual, like any other piece of protoplasm, but they may die, or at all events lose their capacity for reproduction (which comes to the same thing), whilst the ordinary somatic cells are still alive. This commonly takes place in women between the fortieth and fiftieth year. Now, it has been noticed by several observers that children born towards the end of the female reproductive period tend to be feebler than those born whilst the generative organs are in full vigour. Possibly this, in part, may be due to a senility of the maternal tissues which nourish the seed, but it is equally likely to be due to a senility of the seed itself, so that there is some ground for thinking that senescence may be a possible cause of pathological germ variations.

Again, there are certain Infusoria, which, while ordinarily multiplying by fission, from time to time undergo a form of conjugation not unlike that which occurs between the sperm and germ-cells in human beings. It was shown by Maupas that, if this periodical conjugation is prevented, the offspring resulting from subsequent fissions gradually undergoes a form of degradation until