Taking all these observations together, the tendency of pseudopods to move in a spiral manner, the tendency of the ameba as a whole to move in a spiral path when in the flagellate stage, and the wavy path of amebas which is smoothest when in the clavate stage, all these observations seem to confirm the supposition that the wavy path is in reality a flattened spiral, and that the spiral urge in ameba is a very fundamental factor in the process of locomotion. In other words, there is present in ameba an automatic regulating mechanism controlling the direction of movement so that when free from stimulation a spiral path is followed. Where can such a mechanism be located? In organisms of fixed form, such as vertebrates, the mechanism controlling and coördinating locomotion is in the central nervous system. Even in some protozoa (_Euplotes_) a motorium has been found whose function apparently is that of coördinating the action of at least some of the motile organs (Sharp, ’13, Yocom, ’18). But in ameba there is no fixed form. The ameba is continually mixing itself up. No two masses of protoplasm ever occupy the same space relations to each other for more than a moment, excepting perhaps within the nucleus. But the nucleus as a whole is continually changing its position with regard to the rest of the ameba, and almost certainly its position at any given moment in the ameba is the result, not of its own activity, but of the endoplasm and the ectoplasm. A formed nucleus, moreover, is not necessary to concerted movement, for _Protamoeba_, in which no granules of chromatin have been found, and there certainly is no formed nucleus present, moves in a concerted manner, though I am unable to state definitely whether it moves in a wavy path. (I have seen this organism only a few times, and on none of these occasions was I able to make the test). It seems therefore possible that the agency responsible for the movement of amebas in flattened spiral paths can be located at any particular point within the ameba. It seems more likely that this mechanism is a spatial aspect of the intimate colloidal activity occurring in such changes of phase as are associated with the phenomenon of contractility and streaming. Seeing then that movement in spiral paths is possible in animals not possessed of fixed morphology, it becomes of great interest to see whether the spiral paths of free swimming ciliates, flagellates, etc., are similar to those observed in amebas.