Planarians are free-living, freshwater flatworms. They are acoelomates, meaning that they lack a body cavity. Planarians are widely studied for their amazing ability to regenerate as a form of asexual reproduction.
Using the microscope, observe the planarian in the petri dish. How does it move? Does it prefer one part of the petri dish? Use the razor blade to cleanly cut the planarian across the middle.
Observe how each half behaves. Does one move more than the other? Cover the petri dish and place it in a quiet, undisturbed dark area. You will not need to feed the planarians during the regeneration process, but you will need to be sure that there is enough clean water in the dish. After a few days, check on your planarian. If it seems to have formed a lump, it is alive and will regenerate.
If nothing appears to be present, the planarian has died. Check on the dish after one or two weeks. You should have two planarians now, each capable of further regeneration.