everyone is exposed to it, native power of resistance becomes all important.

Direct Effect of Environment on the Germ Cells. Next it should be thoroughly understood that even though the life and habits of the parent do not influence the heritage, these may affect the germ cells directly for good or ill. No one believes that the germ cells are so completely separated from the body cells as to be uninfluenced by them. The germ cells are a part of the organism and their health and vigor are likely to vary with the general health of the organism. Thus poor nutrition may starve the germ cells, and cause them to produce small or weak offspring, but the hereditary constitution remains unchanged. Furthermore, certain poisons like lead or alcohol, at least in large quantities, may affect the germ cells to the detriment of the offspring. The effect may show itself in various ways, and not necessarily in the same way as in the parent. Such a condition is not inheritance, but injury. On the other hand, although injury to the germ cells through the blood is possible, the danger of their permanent deterioration from poor nutrition or from alcoholic poisoning may be easily over-estimated; yet probably the effect of poisons from the social diseases has been underestimated. There is good reason to believe that the germ cells offer strong resistance to moderate deterioration of the body. Pearson made a study of children of temperate and of intemperate parents and found that on the average children of intemperate parents showed no inferiority physically or mentally to those of temperate parents. From the criticisms aroused over this finding, one gathers that his opponents are greatly chagrined to find that the offspring of intemperate parents are not doomed at the start. But nature is not so resentful. In the case of the human species, which has made use of intoxicants from the earliest times, children of intemperate parents may show no signs of degeneracy if they are brought up in a good environment; although, if a parent is a persistent drunkard, the children are likely to inherit such undesirable traits as poor self control, nervous instability, or a degree of feeblemindedness which was probably the basis of the delinquency in

the parent.

Experiments have been carried on to ascertain the effects of alcoholic poisoning upon the lower animals; and, while it is generally agreed that the animals treated degenerated, this result has been interpreted in different ways by different investigators. It is not certain that effects obtained from experiments on animals can be applied to the human species without verification by experiments upon them. The doses of alcohol usually given to animals in these experiments have been so large that the results could have no bearing on the question of moderate drinking. And the human race has made use of intoxicating liquors for such a long period of time that it is only reasonable to suppose that it has become to some extent adapted to the poison. Dr. Jon Alfred Mjöen,' after reviewing the evidence on this subject, concluded that alcoholic poisoning injured both individuals and the race, the injury varying with the strength of the alcohol; but he found no proof that alcohol influenced the offspring when the parent came from sound, healthy stock, although, when he came from tainted stock, Dr. Mjöen believed that use of alcohol prevented any recovery of normality in offspring.

Before leaving the subject of the effects of the environment on the germ cells, it will be worth while to recall the theory given in the previous chapter that external conditions may determine which character of an allelomorph will be dominant. Of course this kind of influence would not be the same thing as the inheritance of an acquired character, but it would be an example of the influence of the environment upon the hereditary process and therefore upon the direction of evolution.

The conclusion to be drawn from the evidence is that, even though acquired traits are not inherited as such, normal and healthy conditions of life for parents are of great importance for the welfare of the offspring from birth. But on the other hand no amount of improvement in the conditions of life of the parents can improve the stock; the heritage will remain the same. The healthy life of the parents will merely insure a normal beginning for offspring already endowed with traits determined by ancestry.

1 Effects of Alcoholism on the Germ Plasm. First International Eugenics Congress, Vol. II.

Problem of the Influence of the Environment Gives Rise to Two Schools of Reform. The second problem of the environment, that of its relative strength and the nature of its influence, is, like the first, a complicated and an unsolved one. As the problem of the inheritance of acquired characters has caused two theories of evolution, so the problem of the relative importance of the environment has given rise to two schools of social reform.

The geneticists believe that inherited characters are of chief importance in determining the nature of the individual, and that the environment, while it is of course a necessary factor in development, will not of itself cause such a wide variation in individuals as that resulting from differences in hereditary traits. Therefore they hold that the art of eugenics, which looks to the improvement of the inherited traits of mankind, is of primary importance to social progress.

The environmentalists on the other hand, while they admit differences in original endowment when extremes like geniuses or the subnormal are considered, believe that the vast majority of mankind are not greatly dissimilar in heritage; and that the differences which do arise are caused by environmental influences, such as early care, education, and opportunity. Accordingly they lay stress on euthenics, the art of perfecting the environment, as the factor of supreme importance for social well being.

True Meaning of the Problem. These two points of view present two sides of an intricate problem. The interrelation of heredity and environment is evident. Inherited traits correspond to the seed; they are latent possibilities. Environment does the work of the soil, the rain, and the sun; it develops the innate characters. The environment cannot develop traits which are not present in the germ cells; but, on the other hand, inherited traits may be suppressed or stunted if the environment is unfavorable. When both nature and nurture, as they have been called, are so evidently indispensable, it may seem unreasonable to speak of their relative importance. Nevertheless a comparison between them is feasible; and it is also eminently worth while, because the question is one of vital importance to

the social worker. The point at issue must first however be made quite clear, for the widespread discussion on this subject has frequently been confused and even irrelevant. Just what is meant then by trying to ascertain the relative importance of two essentials, heredity and environment? First, the problem might narrow itself down to the question of the determination of a particular trait in the individual, such as stature, eyesight, or intelligence; in fact this may finally appear to be the only reasonable way to approach the problem. The answer to this phase of the problem will of course vary according to the character in question. Evidently traits like eye-color are entirely a matter of inheritance, while other physical conditions like diseases, and social acquisitions like good manners, are almost wholly the product of the environment. A system of accurate measurement for all kinds of characters may in time be devised, and the individual then can be pictured as a composite of many traits, some of which are chiefly determined by heredity and others by environment.

Ordinarily, however, this problem has a somewhat different significance to the inquirer. He usually wants to know whether the individual as a whole, and especially whether his mental equipment, is dependent chiefly upon hereditary or upon environmental influences. This general problem may be approached in two ways. One may ask to what degree the adult individual owes his limitations and his achievements to heredity, and to what degree he owes them to environment. Or, stating it the other way around, one may ask if the range of variation produced by the environment is greater or less than the range of variation arising out of inheritance. If, for instance, a number of individuals, sufficiently large to represent all existing differences in natural endowment, were reared in the same environment, would the resulting divergences be greater or less than would be the case, if an equal number of individuals of like inheritance were reared under the varying environmental conditions which actually exist? Although the problem here stated is admittedly complicated and perhaps not capable of exact solution, still investigations have been made which throw some light on the subject.

Galton's Early Studies. Francis Galton ? conceived the idea that valuable evidence concerning the influence of the environment might be obtained from the study of twins. Twins are of two kinds: identical, or those developed from the same ovum, and ordinary twins, the product of different ova. The former are always of the same sex, and were then supposed to bave practically identical inherited traits, though it appears now that they may be similar in some characteristics and quite different in others. Ordinary twins are frequently of opposite sex, and are no more alike than ordinary brothers and sisters. Galton's idea was that if inheritance were of little comparative importance, identical twins would become less and less alike, especially those who had separated early in life and had lived under different conditions, while ordinary twins living under the same conditions would become more alike. Galton studied 35 cases of twins showing remarkable similarity of physical characters, in some cases even in minute details such as form of finger joints and predisposition to have the same ailments; and in at least 16 cases it was ascertained that tastes and dispositions were alike. Although his results were not the same for every case, there was much positive evidence that original similarities continued late in life even under diverse living conditions. Most of the cases of late dissimilarity were attributed by relatives to sickness or accident.

Galton also studied 20 pairs of twins of very dissimilar original traits. In some cases the differences were so marked that the individuals were described as complementary instead of similar. In these cases it was found that the dissimilarities continued, even though the twins lived and were educated under practically identical circumstances.

Modern Psychological Tests. Inasmuch as Galton's method of obtaining data was that of questions through correspondence, his evidence suffered, no doubt, from the defects of the personal equation. Thorndike tried to avoid inaccuracies by measuring twins according to the modern method of mental tests. He measured 50 pairs of twins of different ages on the theory that if the environment were a strong force twins would grow in

1 See Inquiries into the Human Faculty.