412 WM. A. KEPNER AND W. CARL WHITLOCK 
4. A reaction is usually brought about through the coopera- 
tion of both ectoplasm and endoplasm, though the ectoplasm 
alone may carry out a reaction of the second type. 
5. Both the ectoplasm and the endoplasm are highly contrac- 
tile when conditions demand it. 
6. The cutting of an animal like Paramecium into two is pri- 
marily a physical and not a chemical process — digestion setting 
in after the prey has been defragmented. 
7. The process of ingesting food is a reversible one. Food 
half, almost, or wholly ingested may be egested. 
8. An ameba's reactions differ from physical and chemical 
phenomena in that they are quahtative rather than quantitative, 
and are made in the interests of the acting organism. 
LITERATURE CITED 
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Bd. 14. 
Clowes, G. H. A. 1916 a Protoplasmic equilibrium. J. of Phys. Cham., vol. 20. 
1916 b Antagonistic electrolyte effects in physical and biological sj's- 
tems. Science, N. S., vol. 43. 
Grosse-Allermann, Wilhelm 1910 Arch. Protistenkunde, Bd. 17. 
Hyman, Libbie H. 1917 Metabolic gradients in ameba and their relation to 
the mechanism of ameboid movement. Jour. Exp. Zool., vol. 24. 
Jennings, H. S. 1904 Behavior of the lower organisms. New York. 
Kent, W. Saville 1880 A Manual of the Infusoria. London. 
Kepner, Wm. a., and Edwards, J. Graham 1917 Food reactions of Pelomyxa 
carolinensis Wilson. Jour. Exp. Zool., vol. 24. 
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to food. Biol. Bull., vol. 24. 
Leidy, Joseph 1879 Fresh-water Rhizopoda of United States. Washington, 
D. C. 
Loeb, Jaques 1905 Studies in general physiology. Univ. of Chicago Press, 
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Mast, S. O., and Root, F. M. 1916 Observations on ameba feeding on rotifers, 
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Prenard, E. 1905 Fauna Rhizop. du Bassin du Leman, Geneve, Kundig 1902 
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