Pain is one example of a sensation
They have two pairs of main nerve cords organized around a number of paired ganglia. while they don't have a "true brain"-- they have somewhat of a nervous system, composed of the two, or three pairs of nerve cords contained in the visceral mass.
One
substance, other than the secretions from nerve cells, that is used in cell
communication are hormones.
<span>
To
add, <span>a hormone is any member of a class of signaling
molecules produced by glands in multicellular organisms that are transported by
the circulatory system to target distant organs to regulate physiology and
behaviour.</span></span>
The one on the left is ligase and the one in the right on top is polymerase bottom is helicase
