Sea urchins and brittle stars lack eyes, yet nonetheless are capable of vision, or the detection and resolution of spatial images and detail. Their vision, according to what is known today, is mediated through a light-sensing system that extends across the body and is processed via a decentralized nervous system. This is different from two-eyed and even most multi-eyed animals, where light is collected via discrete organs (eyes or eye cups) and processed in a brain or central ganglion. As benthic marine invertebrates, vision may be useful to sea urchins and brittle stars for navigating, finding shelter, or identifying predators. Although photoreceptor cells have been identified in brittle stars, much remains unknown about vision and light responses in both groups and the echinoderms as a whole (sea urchins, brittle stars, sea stars, sea cucumbers, and feather stars). My dissertation examines some of the gaps in this field of inquiry. I investigate (1) the potential ecological correlates of a sea urchin trait thought to mediate spatial vision, (2) how various regions of the urchin body differ in their sensitivity to light, and (3) if brittle stars are capable learning to associate a darkness cue with the presentation of food.