The organization of skeletal tissues in the spines ofEchinus esculentus

Abstract

The relationship between the calcite skeleton and associated cells in the spines of Echinus esculentus is described. The cell bodies lie in channels within the skeleton and cytoplasmic processes extend from them toward the calcite. Swollen regions of the cytoplasmic processes contain organelles such as mitochondria and various vesicles. The plasma membranes of the cytoplasmic processes appear to spread over the calcite surface which is thus topologically intracellular. A considerable portion of the stereom space is extracellular and contains an extracellular fluid and collagen fibres.