I just came across something interesting that I never paid much attention to before.

Note the explanation: ‘Slime moulds are really groups of tiny amoeba which are normally sliding around the forest floor individually. Occasionally they will coalesce into a larger blob. There is no central commander telling the individual cells when to come together or disperse. Like ants, they use pheromone trails. The individual cells release pheromones based on their assessment of the conditions. Using a type of chemical democracy, when the pheromone trail gets intense enough the slime mould cells pile together to form a larger being.’

Here are two links with some crazy pictures of these things.
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The following link shows them in action: [link]