AUTONOMOUS LOCOMOTORY MOVEMENTS 541 



reactions or not. The use of locomotion in free organisms is obvious on the 

 face of it ; where a fixed plant strives to attain a suitable environment and 

 to escape an injurious one by curvatures, free organisms do so by changing 

 their habitat. They frequently attain their object precisely in the same way 

 as in the higher plants, their direction of movement being determined by ex- 

 ternal factors (Lecture XLIII). Amoeboid movements in protoplasts enable 

 these organisms to absorb solid bodies, which they envelop, and so in their 

 case this movement may be regarded as of importance in nutrition. 



Bibliography to Lecture XLII. 



Aderhold. 1888. Jen. Zeitschr. f. Naturw. 22, 310. 



De Bary. 1864. Die Mycetozoen. 2nd ed. Leipzig. 



Berthold. 1886. Studien iiber Protoplasmamechanik. Leipzig, 



BuTSCHLi. 1892. Unters. iiber die mikrosk. Schaume. Leipzig. 



Celakowski. 1898. Bull, de I'Acad. d. sc. de Boheme. 



Clark. 1888. Ber. d. bot. Gesell. 6, 277. 



Correns. 1897. Ber. d. bot. Gesell. 15, 139. 



Engelmann. 1879. Hermann's Handb. d. Physiologie, i. Leipzig. 



EwART. 1897. Journal of the Linn. See. Botany, 33, 123. 



[EwART. 1903. On Protoplasmic streaming. Clarendon Press, Oxford.] 



Fischer, A. 1894. Jahrb. f. wiss. Bot. 27, i. 



Fischer, A. 1901. Archiv f. Entwicklungsmechanik, 13, i. 



Hauptfleisch. 1892. Jahrb. f. wiss. Bot. 24, 173. 



HoFMEiSTER. 1 867. Die Lehre v. d. Pflanzenzelle. Leipzig. 



Jensen. 1902. Ascher-Spiro, Ergebnisse d. Physiologie, i. Wiesbaden. 



JosiNG. 1901. Jahrb. f. wiss. Bot. 36, 197. 



Keller. 1890. Ueber Protoplasmastromung, Diss. Zurich. 



[Kretschmar. 1903. Jahrb. f. wiss. Bot. 39, 273.] 



KtJHNE. 1898. Zeitschr. f. Biol. 36, 425. 



Lauterborn. 1896. Unters. iib. Bau, Kernteilung u. Beweg. d. Diatomeen. 



Leipzig. 

 MtJLLER, O. 1897. Ber. d. bot. Gesell. 15, 70. 

 Nageli. i860. Beitr. z. wiss. Botanik, 2. Heft, p. 96. Leipzig. 

 Pfeffer. 1884. Unters. bot. Inst. Tiibingen, i, 363. 

 Pfeffer. 1890. Pasmahaut (Abh. Kgl. Ges. d. Wiss. Leipzig, 16, 185). 

 Quincke. 1888. Annalen d. Physik, N. F. 35. 

 RiTTER. 1899. Flora, 86, 329. 

 Schafer. 1898. Flora, 85, 135. 

 ScHtJTT. 1899. Jahrb, f, wiss, Bot. 2,2)^ 594. 

 Stahl, 1880. Bot. Ztg. 38, 393. 



Strasburger. 1878. Wirkg, des Lichtes u. d. Warme auf Schwarmsporen. Jena. 

 Verworn. 1901. Allg. Physiologie. 3rd ed. Jena. 

 DeVries, 1885. Bot, Ztg. 43, I. 

 WiLLE. 1902. Biol. Centrbl. 22, 257. 



LECTURE XLIII 



LOCOMOTORY DIRECTIVE MOVEMENTS 



In treating of locomotory directive movements we will confine our atten- 

 tion at first exclusively to non-fixed free-moving organisms (Flagellata, Bacteria, 

 Myxomycetes) and consider protoplasts enveloped in cell-walls later. Just as 

 the directive movements in fixed plants have been spoken of under the general 

 term of ' tropisms ', so the word ' taxis ' has been employed to indicate locomo- 

 tory directive phenomena ; thus we speak of geotaxis, phototaxis, chemotaxis, 

 &c,, according as the direction of the movement is induced by gravity, light. 



