The protozoa are an eclectic assemblage of organisms encompassing a wide range of single-celled and multiple-celled colonial organisms lacking tissue organiza tion, but exhibiting remarkably refined biological behavior. In some modern classifications, they are classified as a subkingdom among the Protista (eukary otic single-celled organisms). Although they are not considered a formal cate gory by some taxonomists and some biologists consider the name inappropriate (inferring that they are the first unicellular animals, although some photosynthe size), it is still convenient to consider this...