You are what you eat.

D ebate over the smallest eye requires a definition of what makes an eye. The answer to this question, generally given by those considered authorities, is that an eye is an organ that receives and recognises light and has the ability to define spatial detail. Specifically, an eye can compare the amount of light coming from different directions. This definition means that an unusual collection of photo-receptors that may perceive light, but cannot tell direction or form of an image, such as those found in the tail of some of the sea snakes, would not be considered an eye. By most definitions then, the plank-tonic dinoflagellate, Erythropsidium, must have among the smallest of eyes, since the creature is only 50–70 mm in diameter. Next to nothing is known about its genetics or visual mechanisms; nevertheless, we do know that this remarkable eukaryote speaks volumes about evolution's creativity and emphasis on vision, although the term ''vision'' goes beyond an eye and must include some degree of interpretation of the image. It is doubtful that this organism interprets any image. Dinoflagellates are protists, or single celled nucleated organisms. Such single celled eukaryotes (organisms that have cells with nuclei) have been traced at least to the Cambrian period (see February 2004 BJO cover essay) or even the Precambrian, but fossil records extend the reign of protists to at least the Lower Middle Proterozoic era, about 1.2 billion years ago. Technically, a protist does not develop from a blastula, so it is not an animal; it does not develop from an embryo, so it is not a plant; it does not develop from spores, so it is not a fungus; but it does contain a nucleus so it is not a prokaryote or bacterium. Protists are varied and most unusual. Some protists, for example, have 100 times the amount of DNA that human cells have. Most zoologists believe protists belong in their own kingdom. Beetles are the most plentiful animal species (July 2004 BJO for review), but the protists are probably more plentiful still. Few would hazard a guess as to how many nucleated algae, water moulds, slime nets, diatoms, and other such species exist, and we surely must have an inadequate understanding and count of this virtually uncountable single celled kingdom. Protists are mainly aquatic, but terrestrial species do exist in moist soils. Single celled they may be, but simple they are not. …