Gruber, K. 1912. Biologische und experimentelle Untersuchungen an _Amoeba proteus_. Arch. f. Protistenk., Vol. 25, pp. 316-376. Hanstein, 1880. Protoplasma. Heidelberg. Harrington, N. R., and Leaming, E. 1900. The reaction of ameba to lights of different colors. Amer. Jour. Physiol., Vol. 3, pp. 9-18. Hartmann, M. 1914. Bemerkungen über _Amoeba lacertae_ Hartmann, eine Antwort an Clifford Dobell. Arch. f. Protistenk., Vol. 34, pp. 336-339. Hegner, R. W. 1918. Variation and heredity during the vegetative reproduction of _Arcella dentata_. Proc. Nat. Acad. Sci., Vol. 4, pp. 283-288. Heidenhain, R. 1863. Stud. d. physiol. Inst. Breslau, Vol. 2, p. 60. Heidenhain, M. 1911. Plasma und Zelle. Bardeleben, Handb. der Anat. d. Menschen. Jena. Hertwig, R. 1902. Die Protozoen und die Ze11theorie. Arch. f. Protistenk., Vol. 1. Hirschfeld, L. 1909. Ein Versuch einige Lebenserscheinungen der Amoeben physikalisch-chemisch zuerklären. Zeit. f. all. Physiol., Vol. 9, pp. 529. Höber, R. 1911. Physikalische Chemie der Zelle und der Gewebe. Leipzig. Hofer, B. 1890. Experimentelle Untersuchungen über den Einfluss des Kerns auf das Protoplasma. Jen. Zeit., Vol. 24, p. 105. Hofmeister, W. 1867. Pflanzenzelle. Holmes, S. J. 1905. The selection of random movements as a factor in phototaxis. Jour. Comp. Neur. and Psychol., Vol. 15, pp. 98-112. Hörmann, G. 1898. Studien über die Protoplasmaströmung der Characeen. Jena. Howell, W. H. 1916. Structure of the fibrin gel and theories of gel formation. Amer. Jour. Physiol., Vol. 40, pp. 526-545. Hyman, L. H. 1917. Metabolic gradients in ameba and their relation to the mechanism of ameboid movement. Jour. Exp. Zoöl., Vol. 24, pp. 55-99. Hyman, L. H. 1918. Bioelectric phenomena. Science, Vol. 48, p. 518. Jennings, H. S. 1899. Studies on reactions to stimuli in unicellular organisms. The mechanism of the motor reactions of paramecium. Amer. Jour. Physiol., Vol. 2, pp. 311-341. Jennings, H. S. 1901. On the significance of the spiral swimming in organisms. Amer. Nat., Vol. 35, 369-378. Jennings, H. S. 1904. Contributions to the study of the behavior of the lower organisms. Washington. Jennings, H. S. 1906. Behavior of the lower organisms. New York. Jensen, P. 1901. Untersuchungen über protoplasmamechanik. Arch. f. d. ges. Physiol., Vol. 87, pp. 361. Jensen, P. 1902. Die Protoplasmabewegung. Ergeb. d. Physiol., p. 42. Jensen, P. 1905. Zur Theorie der Protoplasmabewegung. Anat. Hefte, Vol. 27, pp. 829-858. Kite, G. L. 1913. Studies on the physical properties of protoplasm. Amer. Jour. Physiol., Vol. 32, pp. 146-165. Klebs, G. 1885. Biol. Centralbl. Vol. 5, p. 353.