In the periphery of the granular endoplasm, and adherent to the inner surface of the ectoplasm, is a clearly defined _nucleus_ (n). When most distinctly seen, it presents the appearance of a clear vesicle surrounding a solid and more or less spherical nucleolus. A _contractile vacuole_ (cv) is also uniformly present, located in the endoplasm. The creature has the power of putting out projections (p) from the surface called false feet (_pseudopodia_). Sometimes the protrusion consists of ectoplasm alone, but more commonly endoplasm extends into it, when a current of granules will be observed moving from the more central portions of the Amœba into its protrusion, whilst from some other protrusion that is being withdrawn a similar current may set towards the center of the body, and thus the animal moves, in a creeping manner, from place to place. While moving about in this way the little animal comes across other one-celled creatures, such as _Desmids_ and _Diatoms_, seizing them and forcing them through its ectoplasm into the endoplasm, where the nutritious parts are digested and assimilated. After the animal has taken its prey through its ectoplasm, no break in the continuity of the ectoplasm remains, but the parts immediately come together in a perfect manner. After it has abstracted all the nutriment from its prey, the Amœba casts away from it the parts that are indigestible. [Illustration: FIG. 4.—Rotalia Freyeri: a many-shelled Foraminifer, or a colony of many single-shelled Foraminifera, with pseudopodia extended.] =Foraminifera.= These are little protoplasmic unicellular animals that have the power of secreting for themselves more or less complex envelopes composed of _limestone_. They may be single, as in _Lagena_, or composed of a number of individuals with the shells cemented together as in Globigerina or _Rotalia_ (Fig. 4). They have played a part of vast importance in the geological development of the world. Their myriads of shells remaining at the bottom of seas millions of years after the little protoplasmic bodies have perished, they have been consolidated into vast expanses of limestone rocks, and finally uplifted into such formations as the huge chalk cliffs of England.