Anatomy and classification of sea-urchins
Different parts of the water-vascular system, haemal system, nervous system, digestive tract, and the decalcified stereom of the sea-urchin orders Echinoida, Clypeastroida and Spatangoida have been decalcified, sectioned and stained for light microscopy. Papers describing and discussing the various organ systems and their importance for the classification of see-urchins are in preparation (M. Jensen).