muscular system will suffer, and to some extent remain undeveloped. Or generally, one system of the body can be highly developed only at the expense of some other system, not immediately concerned.

It is true that the more an individual concentrates his efforts on his own intellectual development, the more his sexual system suffers, and the less vigorous his sexual instincts.

And the converse of this is also true, for examples of those with great sexual powers are numerous.

In plant life, this same law is also in operation. If one system in a plant, the woody fibre for instance, takes on abundant growth, the fruit is starved and is less in quality and quantity, and vice versa.

But to what extent does this affect fertility? Sexual power and fertility are not synonymous terms.

The vast profusion of seed in plant and animal life, would allow of an enormous reduction in the amount produced, without the least affecting fertility. Even admitting the application of Spencer's law to sexual vitality, and allowing him to claim that, with the progress of "individuation," there is a decline in sexual instinct, would the fertility of the race be affected thereby?

To have any effect at all on the birth-rate, the instinct would have either to be killed or to be so reduced in intensity as to stop marriage, or to delay it till very late in life.

When once marriage was contracted sexual union once in every two years, would, under strictly normal conditions, result in a very large family.

For according to Mr. Spencer's theory, it is the instinct that is weakened not the power of the spermatozoa to fertilize.

Evidence is wanting, however, to show that there is a decrease in the sexual power of any nation.

France might be flattered to be told that her low birth-rate is due to the high intellectual attainments of her people, and that the rapidly decreasing birth-rate is due to a rapid increase of her intellectual power during recent years.

Ireland and New Zealand would be equally pleased could they believe that their low, and still decreasing birth-rate is due to the lessening of the sexual instinct, attendant upon, and resulting from a high and increasing intellectual power and activity.

The fact is, that the sexual instinct is so immeasurably in excess of the maximum power of procreation in the female, that an enormous reduction in sexual power would require to take place before it would have any effect on the number of children born.

The number of children born is controlled by the capacity of the human female to bear children, and one birth in every two years during the child-bearing period of life is about the maximum capacity.

A moderate diminution in the force of the sexual instinct might lead to a decrease in the marriage rate, but it would require a very serious diminution bordering on total extinction of the instinct to exert any serious effect on the fecundity of marriage.

All that can be claimed for this theory of population is, that, reasoning from known physiological analogies, we might expect a weakening of the desire for marriage, coincident with the general development of intellect in the race.

There are as yet no facts to prove that such weakening has taken or is taking place, nor are there facts to prove that population has in any way suffered from this cause.

If such a law obtained, and resulted in a diminished birth-rate, the future of the race would be the gloomiest possible. An inexorable law would determine that there could be no mental evolution, for the best of the race would cease to propagate their kind. All who would arrive at this standard of mental growth would become barren. And against this there could be no remedy.

One of the main contentions of this work is that the best have to a large extent ceased to propagate their kind, but it is not maintained that this is the result of a biological law, over which there is no control. It can be safely claimed that to Malthus's three checks to population—vice, misery, and moral restraint, the demographic phenomena of a century have added no other. The third check, however, moral restraint, must be held to include all restraint voluntarily placed by men and women on the free and natural exercise of their powers of procreation.

Malthus used the term "moral" in this connection, not so much in relation to the motive for the restraint, but in relation to the result, viz., the limitation of the family. The "moral restraint" of Malthus meant to him, restraint from marriage only, chiefly because of the inability to support a family. It implied marriage delayed until there was reasonable hope that the normal family, four in number, could be comfortably supported, continence in the mean time being assumed. Bonar interpreting Malthus says (p. 53) that impure celibacy falls under the head of "vice," and not of "moral restraint."

To Malthus, vice and misery, as checks to population, were an evil greatly to be deplored in civilized man, and not only did he declare that moral restraint obtained as a check, but he also declared it a virtue to be advocated and encouraged in the interest of society, as well as of the individual.

His moral restraint was delayed marriage with continence. He trusted to the moral force of the sexual passion in a continent man to stimulate to work, to thrift, to marriage; to work and save so that he may enter the marriage state with a reasonable prospect of being able to support a wife and family.

Malthus never anticipated the changes and developments of recent years. He advised moral restraint as a preventive measure in the hope that vice and misery, as checks would be superseded, and that no more would be born into the world than there was ample food to supply. He believed that moral restraint was the check of civilized man, and as civilization proceeded, this check would replace the others, and prevent absolutely the population pressing upon the limits of subsistence.

He saw in moral restraint only self-denial, constant continence, and entertained not a doubt, that the generative instinct would be cheated of its natural fruit. The passion for marriage is so strong (thought Malthus) that there is no fear for the race; it cannot be over-controlled.

The gratification of the sexual instinct, and procreation were the same thing in the mind of Malthus.

But this is not so.

A physiological law makes it possible, in a large proportion of strictly normal women, for union to take place without fertilisation. If it were possible to maintain an intermittent restraint in strict conformity with this law, it would control considerably the population of the world.

It is easier to practice intermittent than to practice constant restraint.

It is just here that Malthus failed to anticipate the future. Malthus believed that "moral restraint" would lessen the marriage rate, but would have no direct effect on the fecundity of marriage.

A man would not put upon himself the self-denial and restraint, which abstinence from marriage implied, for a longer period than he could help.

The greater the national prosperity, therefore, the higher the birth-rate. But prosperity keeps well in advance of the birth-rate; in other words, population, though it still tends to, does not actually press upon the food supply.

If the moral restraint of Malthus be extended so as to include intermittent moral restraint within the marriage bond, then, under one or other, or all of his three checks, vice, misery, and moral restraint, will be found the explanation of the remarkable demographic phenomena of recent years.

Misery will cover deaths from starvation and poverty, the limitation of births from abortion due to hardship, from deaths due to improper food, clothing, and housing; and emigration to avoid hardship.

Vice will cover criminal abortions,