Hydra is a multicellular fresh-water polyp that exhibits remarkable regeneration capabilities,making it an excellent model system for studying animal morphogenesis [1].The animal consists of a single-axis hollow-cylindrical tube(about 5-10 mm long)with a tentacle-ringed head at one end and an adherent foot at the other end.The hydra body-tube is formed by two matrix-adhered(endoderm and ectoderm)epithelial cell layers as shown in Fig.1 [2].Hydra body shape is maintained by a contractile actomyosin cytoskeleton that spans many cells [3].The contractile fibers are longitudinally oriented(along the tube axis)in the ectoderm and circularly oriented in the endoderm.Regenerating hydras use their cytoskeleton to regulate their cells and direct the regeneration process [3].When pieces are excised from hydras,the cytoskeletal pattern survives and becomes part of the new animal.The existing stress fiber pattern generates a small but potent amount of mechanical force that aligns the cells in the first steps of regeneration.This mechanical force can serve as a form of "memory" that stores information about the body plan [3].