Testate lobose amoebae of the genus Arcella can survive after artificial removal of its test,many specimens are capable of building the test de-novo. We investigated this process and found that test-free cells of Arcella in culture remain alive for weeks, they are able to move and feed, but never divide by mitosis. Test-free cells can restore the test in three different ways; usually newly constructed tests are abnormal, but cells restore shape, size and other characteristic features of the test in the next one or two generations of descendants.