Physarum polycephalum - the "many headed slime mold". This eukaryotic organism is a type of amoeba that forms large visible networks, and yet the entire structure is one cell with a contiguous cytoplasm. Physarum is considered an intelligent species because its networks can solve mazes, make decisions, and change behaviors based on past experiences.

See the logo version of one of the below images on the ASM Blog Small Things Considered.