Here there is no specialization among nervous cells, no higher-level control. Later, neurons differentiated into sensory neurons and motor neurons, which control muscle contraction. Also there may be interneurons that establish a network of connections between sensory neurons and motor neurons. In vertebrates, cell bodies of sensory neurons are located part-way along their axons outside the spinal cord, and cell bodies of motor neurons are located within the spinal cord. See an overview of the structure of the nervous system .
Slime molds are plasmodial fungi that live in decaying wood or litter.
Part of their life cycle they live as single-cell organisms. But then they are able to aggregate together and form a fruit body. This example is interesting because metasystem transition starts from aggregation of cells rather than from their multiplication. Then cells become differentiated forming a sporangium on a long column. Fruit body of slime mold 2.7.