Differentiation in multicellular organisms takes a similar course. Every cell, by doubling division of the egg, receives all the rudiments of its kind; of these rudiments, some in one set of cells, others in another, come to develop, according to the part of the whole in which the cells come to lie during the progress of the development, and according to the relations to the whole they come to assume. Thus, here they assume the characters of the external skin; there, they become gland-cells of the intestine; here, muscle-fibres; there, sense-cells or nerve-cells; in one place they serve the whole organism, in the form of blood-corpuscles, as agents for nutrition and respiration; there, becoming connective tissue or bone, they form skeletal elements of the body. Thus, during the course of development, they are forces external to the cells that bid them assume the individual characters appropriate to their individual relations to the whole; the determining forces are not within the cells, as the doctrine of determinants supposes. The cells develop those characters that are suggested by their relation to the external world and their places in the whole organism. But I must insist here that the subordination of the cells to the whole organism, in both multicellular animals and in plants, is much more complicated than that of the units to the human state. In the latter case, the individuals are separate from one another; they are independent organisms and are bound together only in social relations. None the less, consider how in a civilized state the apparently sovereign individual is conditioned in all his circumstances; how each change in the general state exercises an influence on the individual's disposition freedom of will, and method of life (dwelling, food, institutions, health); then reflect how much greater in the animal and the plant is the domination of the whole, and the subordination of the units, as in them cell is directly joined to cell--indeed, in most cases united materially by threads of protoplasm. In such cases the self-sufficiency of the cell as an elementary, living organism is so far prevented, that it becomes a subordinate part, with its function in dependence on the whole. One other point our comparison will make clearer: I refer to the relation of the specific nature of the rudiment to the specific nature of the product of the rudiment. The different organisations and qualities of the communities formed by different animals may be explained by the special characters of the animals forming them. Those of the bee colonies depend on the nature of bees; of ant colonies on the nature of ants; of the societies of men on the nature of men; indeed, in the latter case we see how they differ as they are formed by Italians, Germans, Slavs, Turks, Chinese, or Negroes. Similarly, the specific organisation of the cell determines the kind of animal which may be built up by it.