Inside the display case is a scientific publication and a facsimile drawing made by Santiago Ramón y Cajal in 1917 on the connections between the retina and the brain in cephalopods such as the octopus, squid, and cuttlefish. We have made a comparative drawing with the functioning of the eye of a whale and other vertebrates.
In cephalopods, light enters the eye and directly impacts the photoreceptors, which send an extension to the optic lobe of the brain, where information is processed.
In vertebrates, the retina has more layers of cells where light is processed, and the photoreceptors are in the deeper layers of the retina. Therefore, the light has to pass through the entire retina, reach the photoreceptors, and these send the message back to three other types of cells in the retina until it reaches the ganglion neurons, which send the message, half-processed, through the optic nerve to the brain. Vision in vertebrates begins to be processed in the retina, while in cephalopods it is processed almost entirely in the brain. We can talk about direct vision in cephalopods and indirect vision in vertebrates.
