The task of the workers is to procure all the food necessary for all the individuals of the colony in quantity and quality corresponding to the demand; failing this the whole colony would perish. Now the different persons of the colony need different food, according to their constitution and their functions. Soldiers, for instance, are more powerful than ordinary workers, since they are adapted for fighting, and they therefore require a different kind of food from the weaker workers who are adapted only for other duties. Since the soldiers have evolved from the latter by selection, what we may, for the sake of brevity, call the soldier-food in the common stores of the ants would be drawn upon more lavishly than before, and would therefore disappear more quickly, and, whenever this occurred, those workers which had already brought in this kind of food would be impelled to bring more and more to satisfy the demand for it. But in order to do this they would require to exert themselves more, and would therefore require a larger quantity of food--not of course soldier-food, but the particular kind which their particular qualities demanded. Probably this second importation of food was undertaken by a second kind of worker, for, according to Zehnder, each worker does not carry all the kinds of food; they are divided into legions, each of which has its particular task of food-collecting to fulfil. In the end the storehouse of the ant-colony must contain a provision in which the different kinds of food are in exact proportion to the necessities of the different kinds of persons in the colony. It must alter in its composition again as soon as, in the course of time, one or other kind of person acquires new characters, for these presuppose a new kind of diet. But how are these acquired characters to be transmitted since neither soldiers nor workers reproduce? Zehnder answers this by pointing out that the sexual animals eat _all_ the kinds of nourishment which are accumulated in the stores, that is to say, all the different kinds of food exactly in the proportion in which they have been imported--the proportion in which the different kinds of persons are represented in the colony. Thus the kinds of nourishment which caused the appearance of the newly acquired characters in the non-sexual animals also reached the sexual animals and their sex-cells, and there gave rise to substances which evoke the relevant qualities in their descendants, for instance, in the soldiers, or in the still more modified workers, and so on; and thus we have an 'inheritance of acquired characters.'