. Carnegie Institution of Washington publication. THE MOVEMENTS AND REACTIONS OF AMCEBA. 141 (Fig. 38, anterior end). Further, such particles, after making one or two revolutions, usually become detached and drop oft'. It is thus clear that Amoeba -verrucosa and its relatives have what may be called a rolling motion ; a given spot on the outer pellicula passes forward on the upper surface, downward at the anterior end, remains quiet on the lower surface, passes upward at the posterior end, and again forward. Its movement may be compared directly with the movement of a given point on the circum
. Carnegie Institution of Washington publication. THE MOVEMENTS AND REACTIONS OF AMCEBA. 141 (Fig. 38, anterior end). Further, such particles, after making one or two revolutions, usually become detached and drop oft'. It is thus clear that Amoeba -verrucosa and its relatives have what may be called a rolling motion ; a given spot on the outer pellicula passes forward on the upper surface, downward at the anterior end, remains quiet on the lower surface, passes upward at the posterior end, and again forward. Its movement may be compared directly with the movement of a given point on the circumference of a wheel that is rolling forward. A diagram of the movement of a particle on the surface as it would appear in a side view is given in Fig. 40. Certain details of the movements are interesting, and may best be brought out by description of specific observations. In one case two small particles had become attached, a short distance apart, to the surface of a specimen of Amoeba sphczronucleolus. They were at first side by side and a little to the right of the middle line, one somewhat farther to the right than the other (Fig. 41). They moved forward in parallel courses, and reached the anterior edge at the same time, passing over the edge and to the under surface. It now required two and one- half minutes for the Amoeba to pass over p them, during which time they remained nearly or quite at rest. They then moved upward to the upper surface and forward again. The one nearer the middle line moved a little faster than the other, reaching the anterior edge in two and three- quarter minutes, while the lateral one required three minutes. Both emerged at the posterior end again at the same time, the central one having remained quiet three and one-fourth minutes, while the lateral one had been three minutes at rest. The next forward course required, respectively, but one and one-half and two minutes, the central particle moving the more rapidly. The two particles were no longer
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