Advances in Comparative Physiology and Biochemistry

The extent to which environmental conditions mediate the behavior of certain organisms of basically cellular constitution, e.g., the protozoa, has been the subject of considerable investigation for more than two hundred years, ever since the classic experimental observations of Kühne (1864), Engelmann (1869, 1879, 1906), and Verworn (1889a,b, 1896, 1913) on a variety of microorganisms. Prominent among such investigations have been numerous researches on amebas. As organisms of cellular constitution having morphological organelles of temporary duration, e.g., their pseudopods, water-expulsion vesicles ("contractile vacuoles"), and gastrioles ("food vacuoles"), the amebas have been considered as perhaps the more primitive and unspecialized of cells available for such studies. Therefore, their motile responses to environmental conditions, natural or experimental, have been assumed to be biologically basic responses, indicative of the fundamental responses upon which the behavior of higher animals may be constructed biologically, and perhaps evolutionarily as well.