1. Various flagellates and small ciliates stick to the axopods of Actinophrys. Contact with the base of an axopod or with the body surface leads to the outgrowth of a food funnel, by which the prey is ultimately surrounded.
2. If a fine probe or micropipette touches the body surface or the base of an axopod, a small cup may grow out over it, investing it closely, but the instrument is soon released. A squirt of tap water from a micropipette may also provoke the outgrowth of a small lobe or cup, or local pinocytosis.
3. Contact with, or a squirt from, a micropipette containing a solution of egg albumin provokes a more extensive reaction. The micropipette usually becomes invested extensively. The micropipette is drawn into the body and held there for up to an hour.
4 Immersion in egg albumin solution leads to a temporary spreading and lobulation of the axopod bases, and later a ‘skin’ may separate from the body surface. Skin formation is more pronounced in serum albumin solution, and may also be induced by γ-globulins and gelatin.
5. On treatment in vivo with toluidine blue or thionine a violet layer in the body surface separates as a pinkish violet or violet skin, leaving the body surface unstained.
6. There is evidence that the skin-forming substance is associated directly or indirectly with the maintenance of cell shape.
Ca2+-dependent nuclear contraction in the heliozoon Actinophrys sol