His studies of nutrition in one-celled animals during the 1930's contributed to the discovery that vitamins affect growth.

Plants and one-celled animals, after all, without a trace of anything we would recognize as a nervous system nevertheless react to chemical stimuli.

Those one-celled animals have a bewildering array of minuscule shells.

These microscopic one-celled animals are content to crawl through their environment, absorbing whatever food they come across.

He looked at Daniel and explained, "There's big one-celled animals here.

When an infusion of coffee from the food shop was added to the liquid environment of one-celled animals, they died.

"When primitive one-celled animals first began to cooperate," he said to the Master, "they did not at once form a man."

Even in the one-celled animals there had been a mating.

It's ironic in a way, having little one-celled animals telling us what happened to the biggest life form ever.