I fed the worms starch grains and the worms had some problems digesting them. The potato starch grains light up under polarized light. I put a polarizing filter on the lamp of the microscope and one on top of the dish with the worms. One can see the starch grains move through the digestive system of the worm. The name of the worm is Aeolosoma and it can be found in fresh water (eg ponds etc).