Pattern of birefringence in the giant amoeba, Chaos carolinensis

Abstract

1. 1. The giant amoeba, Chaos carolinensis, shows a dynamic but characteristic pattern of weak birefringence demonstrable in polarized light photomicrographs only after light scattering inclusions have been removed 2. 2. The plasmalemma, presumably because of its ‘fringe’ layer, has slightly stronger birefringence than the membranes of vesicles. The slow axis of transmission is parallel to the membrane surface. 3. 3. The streaming endoplasm always shows positive axial birefringence (slow axis parallel to the stream) along its entire length. When streaming stops, this birefringence decreases. 4. 4. The ectoplasmic tube has weaker birefringence and its sign varies locally. The peripheral region of the ectoplasmic tube is usually positively birefringent. Negativebirefringence, if observed, has a characteristic patchy distribution localized mostly adjacent to the endoplasmic stream. 5. 5. Formation of a new pseudopod results in the rapid establishment of the pattern of birefringence described above. When the pseudopod begins to retract, the entire pattern fades until it disappears in the light-scattering noise of remaining cytoplasmic inclusions. 6. 6. The pattern of birefringence is the only reliable evidence now available on the deployment and orientation of submicroscopic linear elements in the cell and their behavior during amoeboid movement. The results are entirely consistent with the frontal contraction theory of amoeboid movement.