In previous divulgations 13th and 17 th entitled " The eyes and central nervous system origin” and " Brainstem ganglionic chains” we wrote “ First ring ganglions are transversely connected to each other and  longitudinally with the following ring ganglions, forming a structure denominated "roped chain or rope ladder" and  " there is established a direct biochemical relation between the first cranial ganglions of the marine annelids and the first cranial  ganglions of actual vertebrates (their eyes) ". In the attached photos it can be observed the structure of the ganglionic chain and the connection between the first cranial ganglions and the snails’ eye.