M. Condorcet seems to have entertained some very hopeful ideas as to the perfectibility of the human frame, and to have thought that though man would not become absolutely immortal, yet that the duration between his birth and his natural death would increase without ceasing, would have no natural term, and might properly be expressed by the term indefinite. Malthus demurs to these speculations. He thinks that the average duration of human life will, to a certain extent, vary from healthy or unhealthy climates, from wholesome or unwholesome food, from virtuous or vicious manners, and from other causes; but it may be fairly doubted whether there has been really the smallest perceptible advance in the natural duration of human life since we had any authentic history of man. “What can we reason but from what we know?” “The capacity of improvement in plants and animals, to a certain extent, no person can possibly doubt. A clear and decided progress has already been made, and yet I think that it would be highly absurd to say that this progress has no limits.... The error does not seem to lie in supposing a small degree of improvement possible, but in not discriminating between a small improvement, the limit of which is undefined, and an improvement really unlimited. As the human race could not be improved in the same way as the domestic animals, without condemning all the bad specimens to celibacy, it is not probable that an attention to breed should ever become general.” Here, again, we prefer the injunction of Professor Mantegazza to consumptive parents: ‘Amate, ma non generate’ (‘Marry but do not reproduce’). The speculations of Condorcet seem, to a certain extent, to have been revived in modern days by Mr. H. Spencer and Dr. B. W. Richardson. The former of these distinguished authors seems to look forward to a time when the wants of mankind shall by the process of evolution become equated to their powers of acquiring food, without calling in the will; and Dr. Richardson seems to look forward to a far greater longevity for individuals of the human species than has been experienced in its past history.