358 LOCOMOTORY AND PROTOPLASMIC MOVEMENTS 



temporary retardation of the movement of swarm-spores of Diatoms and 

 of Oscillaria^-. 



Contact and other mechanical agencies produce a transitory stoppage 

 of the cilia of Chlamydomonas pulvisculus z , and the cilia of many 

 locomotory organisms seem to possess a certain contact irritability, 

 such as appears to be exhibited by Stylonychia and other Infusoria which 

 run about over the substratum 3 . According to Bordet 4 , the antherozoids 

 of Fucus have a ' thigmotaxis ' or ' haptotaxis ' of this kind, and a similar 

 but feeble irritability is supposed by Massart to be shown by Spirillum 

 undula. Whether, as in the case of tendrils, the solid substratum directly 

 exercises a contact -stimulus is not perfectly certain, since the Infusoria 

 mentioned may also creep on the surface of the water 5 . The stoppage 

 of movement in the cilia of Chlamydomonas produced by mechanical shocks 

 is, however, comparable with the shock-movements of the leaves of Mimosa 

 pudica in so far as both are irritable responses to stimuli, but whether 

 still other special irritabilities may exist among these lower forms is an 

 open question. 



Wounding and injuries, however produced, always exert a certain 

 influence on movement, and frequently an injury excites or causes an 

 acceleration of protoplasmic streaming, and may also produce various 

 traumatic aggregations of the cell-contents. 



After a few observations by Frank and Velten, Keller and Hauptfleisch estab- 

 lished the fact that the active streaming shown in sections often does not exist in the 

 intact plant, but is produced, or accelerated when pre-existent, by the injury, and in 

 part also by other stimuli 6 . Streaming is, for instance, absent from the intact leaves 



1 linger, Die Pflanze im Momente d. Thierwerdung, 1843, p. 67; Strasburger, Wirknng d. 

 Lichts und d. Warme auf Schwarmsporen, 1878, p. 6 ; Engelmann, Bot. Ztg., 1879, p. 55 footnote. 



3 Pfeffer, Unters. a. d. hot. Inst. zu Tubingen, 1884, Bd. I, p. 444; Massart, La sensibilite' tactile 

 chez les organismes inferieures, 1900 (extract from the Journal public par la Soc. royale d. sci. med. 

 et nat. de Bruxelles). 



3 Pfeffer, Unters. a. d. bot. Inst. zu Tubingen, 1888, Bd. II, p. 618; Venvorn, Psycho-physiolog. 

 Protistenstudien, 1889, p. 90 ; Massart, 1. c., 1900 ; Jennings, Journal of Physiology, 1897, Vol.xxi, 

 p. 298 ; American Naturalist., 1901, Vol. XXXV, p. 372 ; Putter, Archiv f. Anatomic u. Physiologic, 

 physiolog. Abth., Supplement, 1900, p. 243. 



* Bordet, Bull, de 1'Acad. royale de Belgique, 1894, 3" sen, T. XXVII, p. 889. On the thigmo- 

 taxis of certain animal spermatozoids see Dewitz, Pfliiger's Archiv f. Physiologic, 1886, Bd. xxxvni, 

 p. 358 ; Centralbl. f. Physiol., 1903, Bd. XVII, p. 89 ; Massart, Bull, de 1'Acad. royale de Belgique, 

 1888, 3 e ser., T. XV, Nr. 5 ; Buller, Quarterly Journal of Microscopical Science, 1902, Vol. XLVI, 

 p. 145. 



5 Massart, 1. c., p. 7. Massart concludes that the surface-tension film may act as a solid, and 

 considers the accumulation of Chromulina Woroniniana at the surface to be the result of tactic 

 stimulation. Even a very slight accumulation of minute solid or liquid floating particles at the 

 surface would be able to exercise tactic stimulation. 



6 Frank, Jahrb. f. wiss. Bot., 1872, Bd. viil, pp. 220, 292 ; Velten, Bot. Ztg., 1872, p. 672 ; 

 I. Keller, Ueber Protoplasmastromung im Pflanzenreich, 1890; P. Hauptfleisch, Jahrb. f. wiss. Bot., 

 1892, Bd. xxiv, p. 190; De Vries (Bot. Ztg., 1885, p. i) from his observations on sections con- 

 cluded that streaming was a much more common and normal occurrence than it actually is. The act 



