The tube feet that are not busy pulling the urchin along appear to be engaged in a slow dance. They look a little blurry, because they were moving when the picture was taken. You will see how long and thin they are. Now compare these tube feet to the scanning electron picture of a single tube foot below.

This is a scanning electron micrograph, or what is usually called an SEM image, of a sea urchin tube foot. You will notice the suction-cup end. Because the tube foot is retracted (pulled back) there are a large number of folds in the long part of the foot.

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