Arthropods....

Arthropods are animals with a hard external skeleton like a suit of armor. The skeleton is jointed to allow movement. Arthropods have evolved in a different way to vertebrates. Instead, they have a nerve cord running along the underside of their body, and small thickenings of this nerve cord instead of a brain. Arthropods have efficient eyes, but these work in a different way from those of vertebrates. Arthropods such as spiders may have many eyes.