. General physiology; an outline of the science of life. 148 GENERAL PHYSIOLOGY runs away. A second rare case of this kind is afforded by Vavipy- rella Spirogyrce. The amoeba of this species applies itself to a healthy Spirogyra, bores through the cell-wall and devours the slowly escaping primordial utricle together with the chlorophyll-^ bands. It seems to be able to satisfy its hunger upon Spirogyra ; (Fig. 48.) But we need not search so far. In the human body there are cells that behave similarly. As Metschnikoff ('92) has shown by his researches extending over many years, the leu
. General physiology; an outline of the science of life. 148 GENERAL PHYSIOLOGY runs away. A second rare case of this kind is afforded by Vavipy- rella Spirogyrce. The amoeba of this species applies itself to a healthy Spirogyra, bores through the cell-wall and devours the slowly escaping primordial utricle together with the chlorophyll-^ bands. It seems to be able to satisfy its hunger upon Spirogyra ; (Fig. 48.) But we need not search so far. In the human body there are cells that behave similarly. As Metschnikoff ('92) has shown by his researches extending over many years, the leucocytes or white blood-corpuscles, the amoeboid wandering-cells, devour and digest certain forms of bacteria present in the body, while they scorn and even directly avoid other bacteria; likewise, intestinal. Fig. 48 —Vam'pyrella Spirogyne boring into and suck- ing out a Spirogyra-ce^. A. The Spirogyra-ceM is pierced and the contents are passing out into the VaiiipyreUa. B. The Spirogyra-QoW is completely emptied. At * a ceU that has been pierced and emptied. (After Cienkowski.) epithelium-cells, as has been seen, devour only fat-droplets, while they behave wholly passively toward other small particles that are brought into the intestine, such as granules of carmine. Finally, another very interesting phenomenon, which has to do with the ingestion, not of food, but of substances that likewise play a rdle in the life of the organisms in question, has also frequently been referred to, although incorrectly, as a power of selection on the part of the cell. This is the ingestion of material for shells and capsules on the part of certain shell-bearing rhizopods. The Difflugice, which are unicellular fresh-water Bhizopoda whose naked protoplasmic bodies are fixed in a very delicate urn-shaped or flask-shaped capsule, take up the material for their tiny dwellings with their finger-like pseudopodia out of the mud of the pools and lakes at the bottom of which they The structural
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