You put the difficulty of the first modification of the first protozoon admirably.
"More Letters of Charles Darwin" by Charles Darwin
To it energy is available which is denied to the protozoon.
"The Birth-Time of the World and Other Scientific Essays" by J. (John) Joly
For we may look at this matter in another light, and say our exuberant protozoon has shed a daughter, and remains.
"Certain Personal Matters" by H. G. Wells
For the body of a many-celled Wheel Animalcule or Rotifer is no bigger than many a Protozoon.
"The Outline of Science, Vol. 1 (of 4)" by J. Arthur Thomson