How do the nervous system of clams and octopuses differ?

Answer: Clams don't have a nervous system and octopuses have a highly complex nervous system.

Explanation: Clams do not have a central nervous system and when compared to the ones of squids or octupi, seems like they are not even living. Clams are stationary for most their lifes, only moving when forced to. However, when a disturbance is present, the clams close quickly into a defensive position, with their hard calicum shells protecting their inner works.