Ineed information on gelly fish for my assiment me

** in your own words **

Jellyfish use their tentacles to sting. Most are harmless to humans but stings from some species, such as the box jellyfish, can be very painful and sometimes kill. Lacking brains, blood, or even hearts, jellyfish are pretty simple critters. They are composed of three layers: an outer layer, called the epidermis; a middle layer made of a thick, elastic, jelly-like substance called mesoglea; and an inner layer, called the gastrodermis. 

If you need more information let me know (also sorry if i misspelled words) 

Use the formula: (n-2)×180, where n is the number of sides(18-2)×180= 28800, now this is the full exterior angle of 18-gon so you divide it by 18.28800÷18=160