Many single-celled forms of life exist, but no known forms of animal life have 2, 3, 4, or 5 cells (a). Known forms of life with 6–20 cells are parasites, so they must have a complex animal as a host to provide such functions as respiration and digestion. If macroevolution happened, one should find many transitional forms of life with 2–20 cells—filling the gap between one-celled and many-celled organisms.
a. E. Lendell Cockrum and William J. McCauley, Zoology (Philadelphia: W. B. Saunders Co., 1965), p. 163.
Lynn Margulis and Karlene V. Schwartz, Five Kingdoms: An Illustrated Guide to the Phyla of Life on Earth (San Francisco: W. H. Freeman and Co., 1982), pp. 178–179.
Perhaps the simplest forms of multicellular life are the Myxozoans, which have 6–12 cells. While they are quite distinct from other multicellular life, they are even more distinct from single-celled life (kingdom Protista). [See James F. Smothers et al., “Molecular Evidence That the Myxozoan Protists are Metazoans,” Science, Vol. 265, 16 September 1994, pp. 1719–1721.] So, if they evolved from anywhere, it would most likely have been from higher, not lower, forms of life. Such a feat should be called devolution, not evolution.
Colonial forms of life are an unlikely bridge between single-celled life and multicelled life. The degree of cellular differentiation between colonial forms of life and the simplest multicellular forms of life is vast. For a further discussion, see Libbie Henrietta Hyman, The Invertebrates: Protozoa through Ctenophora, Vol. 1 (New York: McGraw-Hill, 1940), pp. 248–255.
Nor do Diplomonads (which have two nuclei and four flagella) bridge the gap. Diplomonads are usually parasites.
[http://www.creationscience.com/onlinebook/LifeSciences23.html >From “In the Beginning” by Walt Brown ]