The main features of the movements of diatoms are very similar to those of Oscillatoria. Müller (’89, ’97, ’99) has shown that the gliding movements of diatoms are not due to the ejection of water, but to the streaming of protoplasm on the outside of the shells. Foreign particles are carried by these shallow streams of protoplasm in quite the same manner as by the surface film of the ameba. And there seems to be no evidence against the assumption that these shallow streams, at least the surface films over them, owe their movement to changes in surface tension. Desmids also glide about slowly, leaving a track of mucus behind. Only one explanation for locomotion has been advanced, and that is that it is due to the secretion of mucus (Klebs, ’85). This explanation is likely to be as wide of the mark as the similar explanation in the case of Oscillatoria. There is no question concerning the excretion of mucus, but the source of the locomotive energy is probably here also surface energy, though the observational data are too few to try to locate the regions where the changes in tension occur. It has been a matter of considerable surprise to me to find that the so-called “crawling” euglenas, in addition to the diatoms, desmids, Oscillatoria, Beggiatoa and perhaps other forms of life such as the Gregarinidas, also possess extra-cellular films which carry particles as do amebas and Oscillatoria, and move about through the agency of this film. The film travels spirally around the euglena as it does in Oscillatoria filaments. In at least two species the film moves parallel to the spiral striations on the outer surface. In one species no spiral striations could be detected, although the film moved spirally. The species of euglenas in which these movements were observed, were not identified. The character of the movement of the euglenas is very similar to that of the diatoms excepting that most of the diatoms do not revolve on their longitudinal axes. The movement of particles on the surface film of euglenas is quite like that in Oscillatoria, though it is only under exceptional circumstances that one can see particles attached to the surface film. The movement of the particles indicates that the surface film moves from the anterior end toward the posterior end, but whether the “spine” is to be included was not definitely determined. The degree of cohesiveness of the film is high, for locomotion is rapid, even if only a small part of the posterior end is in contact with the substratum, as when moving over an Oscillatoria filament. To one who has seen the movements of the surface films of amebas, diatoms and Oscillatorial filaments, the most reasonable conclusion seems to be that the cause of locomotion in crawling euglenas is the same as that in Oscillatoria and diatoms.