Q. How does photosensitivity in annelids, cnidarians and worms differ from insects, cephalopods and vertebrates?
In the first mentioned group of animals there are photoreceptor cells organized in diffusely or ocelli dispersed in the body these animals do not form images.
In the animals of the second group the photoreceptor cells are part of more sophisticated structures, the eyes able to form images and to send them to the nervous system.