Worms do not have eyes but they have light- and touch-sensitive organs (receptor cells). These cells help them sense differences in light intensity and to feel vibrations in the ground. Earthworms have bilateral symmetry. This means that if you cut the earthworm down the centerline, the left side of the body would be identical to the right side. They do not have a backbone. Insects, sea stars, spiders, jellyfish, and millipedes are other examples of invertebrate animals.