Planaria Regeneration

Planaria are flatworms (Platyhelminthes) and more complex than hydras. They have a remarkable regenerative ability. When a planaria is cut in two, each fragment will regenerate a complete animal.

In fact, a single planaria can be cut into dozens of small pieces, and each can regenerate a complete new animal. This amazing ability seems to be related to the relative abundance of stem cells called neoblasts.