planarian regenerate by sexual/asexual reproduction
It is in their genetic code to do so.
you can make them freak out by touching them. they start swimming in a different direction and sometimes run into things because they can only see light not details.
totiotency of cells
Any living thing that moves and breathes is an animal inclulding palnarions and inscets etc.
They vary from 1/8 inch to 1 inch long.