Amoeboid movement is the characteristic of some protozoans, slime molds and vertebrate white blood cells. The movement of these is due to cytoplasmic streaming, change in cell shape and extension of pseudopodia. These changes are easily observed under the microscope, but the mechanisms involved in activating the movement are not well understood. When an amoeba has to move. it stretches its arm-l.ike extensions, the pseudopodia, into the required direction and its cytoplasm flows into the newly formed pseodopodia. The newly formed pseudopodia gradually extend and enlarge so that the entire cell occupies the space where previously only a small pseadapodium began to form.
As the cell moves, new pseudopodia are formed in the direction of the movement, while the posterior parts are withdrawn. It is not known with certainty how the extending and retracting of the pseudopodia takes place. It appears that there is a transaction of the regions of the cytoplasm from fluid-like sol to semi solid gel state. Now we shall study how amoeboid movement is accomplished by transactions of cytoplasm from sol to gel state.