This experiment requires balloons and yarn. Give students a balloon and ask them to blow it up and tie off the end. Give them a 5-12 inch piece of yarn and ask them to tie it to the end. When the students hold the balloon (animal) by the top and let the stinging cells (yarn) hang down, they can sweep the stinging cells across their arms. Their arms will become paralyzed for consumption. If the students turn the balloon upside down, the yarn will fall down to show the knot which is a good example of what the mouth looks like on a stinging celled animal.