En mask som delas dör.
Den har mun i ena änden och anus i andra, med div organ däremellan.

Men frågeställningen kan iofs föras över på sjöstjärnor.
Om en sjöstjärna blir av med en arm, växer det ut en ny.
Och ibland växer det ut en ny sjöstjärna på den saknade armen.

Har sjöstjärnor nåt centralt nervsystem? Tror inte det men inte säker?

Nervous system

While starfish lack a centralized brain,[36] their bodies have complex nervous systems which are coordinated by what might be termed a distributed brain. They have a network of interlacing nerves, a nerve plexus, which lies within, as well as below, the skin.[27] The oesophagus is also surrounded by a central nerve ring, which sends radial nerves into each of the arms, often parallel with the branches of the water vascular system. These all connect to form a brain. The ring nerves and radial nerves coordinate the starfish's balance and directional systems.[31]

Although starfish do not have many well-defined sensory inputs, they are sensitive to touch, light, temperature, orientation, and the status of water around them.[37] The tube feet, spines, and pedicellariae found on starfish are sensitive to touch, while eyespots on the ends of the arms are light-sensitive.[38] The tube feet, especially those at the tips of the rays, are also sensitive to chemicals, and this sensitivity is used in locating odour sources such as food.[39]

The eyespots each consist of a mass of ocelli, each consisting of pigmented epithelial cells that respond to light and narrow sensory cells lying between them. Each ocellus is covered by a thick, transparent cuticle that both protects it and acts as a lens. Many starfish also possess individual photoreceptor cells across their bodies and are able to respond to light even when their eyespots are covered.[35]

Men frågan är vad händer med jaget vid delning?