Two planaria come together to fertilise each other's eggs. The eggs are encased in shell-like cocoons that are left in the water to hatch. But planaria can also split in half with a crosswise division. The front half grows a tail. The tail grows a new head.
Planaria have two tiny eyes on the head.
They dislike both light and heat. They will move the shadows or under objects. They move away from warm water or any heat. Most need water with a good oxygen supply and will die in polluted water easily. Sense organs on their heads help them find their foods.