These droplets would `` grow '' by fusion with other droplets , and `` reproduce '' through fission into daughter droplets , and so have a primitive metabolism in which those factors which promote `` cell integrity '' survive , those that do not become extinct . These droplets would `` grow '' by fusion with other droplets , and `` reproduce '' through fission into daughter droplets , and so have a primitive metabolism in which those factors which promote `` cell integrity '' survive , and those that do not become extinct .