Photosensitivity in annelids-cnidarians and worms

Question

How does photosensitivity in annelids, cnidarians and worms vary from insects, vertebrates and cephalopods?

Answer 1

In the first mentioned group of the animals there are photoreceptors cells organized in ocelli or diffusely dispersed in body. These animals don’t form images. In the animals of second group the photoreceptor cells are division of more sophisticated structures, the eyes, capable to form images and to send them to nervous system.