What four body plan innovations were found in an ancient flatworm

Four innovations are central nervous system, eyes, bilateral and hermaphrodites.

Explanation:

Innovations found in an ancient flatworm were the presence of central nervous system means head and a brain. The head had eyes which is the first in the animal world. Their body is bilateral means equally divided into two parts. They are also hermaphrodites means having male and female on a single organism which was not present at that time of animals.

after receiving a stimus, the sensory receptors send(s) signals to the appropriate area of the body.  

the must be sensory neurons.  

hope its .