adventurous, the nomadic, and those who have fewer ties; it would be difficult to demonstrate that they are superior to those who, having settled positions at home, or family obligations, fail to volunteer. The greatest damage appears to be done in such wars as those waged by great European nations, where the whole able-bodied male population is called out, and only those left at home who are physically or mentally unfit for fighting--but not, it appears to be thought, unfit to perpetuate the race. Even within the army of one side, lethal selection is operative. Those who are killed are by no means a haphazard sample of the whole army. Among the victims there is a disproportionate representation of those with (1) dauntless bravery, (2) recklessness, (3) stupidity. These qualities merge into each other, yet in their extremes they are widely different. However, as the nature of warfare changes with the increase of artillery, mines, bombs, and gases, and decrease of personal combat, those who fall are more and more chance victims. In addition to the killed and mortally wounded, there are many deaths from disease or from wounds which were not necessarily fatal. Probably the most selective of any of these three agencies is the variable resistance to disease and infection and the widely varying knowledge and appreciation of the need for hygienic living shown by the individual, as, for instance, by less reckless drinking of unsterilized water. But here, too, in modern warfare, this item is becoming less selective, with the advance in discipline and in organized sanitation. The efficiency of selection will be affected by the percentage that each side has sent to the front, if the combatants are either above or below the average of the population. A nation that sends all its able-bodied males forward will be affected differently from its enemy that has needed to call upon only one-half of its able-bodied men in order to win its cause. Away from the fighting lines of the contending sides, conditions that prevail are rendered more severe in many ways than in times of peace. Poverty becomes rife, and sanitation and medical treatment are commonly sacrificed under the strain. During a war, that mitigation of the action of natural selection which is so common now among civilized nations, is somewhat less effective than in times of peace. The scourge of typhus in Serbia is a recent and graphic illustration. After a war has been concluded, certain new agencies of inter-group selection arise. The result depends largely on whether the vanquished have had a superior culture brought to them, as in the case of the Philippines, or whether, on the contrary, certain diseases have been introduced, as to the natives of the New World by the Spanish conquerors and explorers, or crushing tribute has been levied, or grievous oppression such as has befallen Belgium.