Sea Urchins

A closeup look at sand urchins and rock urchins At the seashore a man digs up a sand urchin We look closely He sets it back in the sand and it burrows out of sight Its intestines take nutrients out of sand Using magnification 200000 times normal size we see a rock urchins spines with suckers on the end a drawing illustrates how they work A sea urchin walks toward a rock We see threefingered jawspedicellaria at the end of flexible stemstake in algae and other bits We also see cilia less than 0001 ml in length their motion constant creating whirlpools On the shore again we watch the setting sun Occasional titles in French tell us what to watch for