In your own body, don't all the different cells know what to do? When to grow and when to stop growing? When to form certain substances and when not to, and when they form them, just how much to form, neither more nor less? Each cell is, to a certain extent, an independent chemical factory, but all draw from a common fund of raw materials brought to it by a common transportation system, all deliver wastes into common channels, and all contribute to an overall group consciousness.