origin of races, of languages, of the stars, etc. is a legitimate object of study, the origin of plants and animals is an inquiry of an entirely different nature,—a subject about which man can learn nothing. Those who are continually referring to the mysteriousness of Life as an objection to its study, seem to forget that the ultimate causes of all other phenomena, such as the falling of an apple, the combining of elements, the crystallization of a salt, etc., are equally mysterious. The forces by which these phenomena are brought about are studied in their effects; and the laws according to which these effects are produced belong to Astronomy, Chemistry, Crystallography. But of the cause or essence of gravitation we know nothing. We can only say that bodies attract one another according to a certain law. Equally unknown is the ultimate cause of crystallization. We can only say that in saline solutions, under favorable conditions, according to law, geometrical forms are produced. Compare now the growth of a crystal with that of a plant or an animal. If a seed be sown and it attract certain elements from the soil, a definite form, a plant, is produced; in the same way the chick results from the embryo attracting the material of its future body from the yelk. The laws governing the forces by which these effects are brought about, the phenomenaof the growth of a plant or of an animal, are as legitimate objects of study as the growth of a crystal. The nature of the inquiry is the same: the study of the growth of a crystal differing from that of a plant or an animal not in kind but only in degree; the investigation being in each case the redistribution of matter, for there is nothing in the crystal that did not pre-exist in the saline solution, nothing in the plant that was not derived from the seed or the soil, nothing in the chicken that did not pre-exist in the egg or in the air. The ultimate cause of the so-called Vital Force is as unknowable as the cause of all other kinds of Force. The laws, however, by which the effects of the so-called Vital
