Figure 13. Amoeba sphaeronucleosus. In locomotion. Note the nucleus, contractile vacuole, ectoplasmic ridges. This ameba is not known to form pseudopods. Length, 120 microns.
Of the more common species of amebas, those with the firmer ectoplasms are the most favorable for studying the movements of the outer layer. We may therefore first take up several observations on Amoeba sphaeronucleosus ([Figure 13]). This ameba resembles the more common A. verrucosa. It is about 120 microns long and is usually of an oval shape in locomotion. It is more active and less disturbed by jars than verrucosa.
[Figure 14] represents a sphaeronucleosus with a small particle attached to the middle of the upper surface of the ameba. As the ameba moves forward, shown by successive outlines, the particle likewise moves forward, but, as will be observed, at a more rapid rate. Measuring the distance from particle outline 1 to 4, and from ameba outline 1 to 4, it is seen that the rate of movement of the particle compares with the rate of movement of the ameba as 2.48 to 1.
Figure 14. Illustrating the movement of a particle on the upper surface layer of an Amoeba sphaeronucleosus. Length of the ameba, 120 microns.
