CILIARY MOVEMENT 269 



zoospores should be considerably retarded in viscous media, and should 

 cease in moderately firm gelatine 1 . 



Cilia are living plasmatic organs which in some cases may protrude 

 through an investing cell-wall 2 . They arise, therefore, in the same way 

 as pseudopodia, and like these may be retracted in certain cases 3 . When 

 highly specialized, however, they are usually thrown off when injured, 

 but undergo the deformations characteristic of living protoplasm through- 

 out their whole substance. Whether cilia are connected with the nucleus 

 or with centrosomes or with special blepharoplasts (cilium formers, or 

 prominences bearing cilia), they possess a certain degree of autonomy 

 like other plasmatic organs. Hence ciliary movement may continue for 

 a time on separate non-nucleated fragments of a cell, or even on isolated 

 cilia 4 . Nevertheless attached cilia must be partially governed by the 

 cell to produce harmonious movement, although it is not certain whether 

 each cilium is isochronous or may vary its phases of movement within 

 certain limits. It is not necessary that the cilia should all be exactly 

 isochronous to produce the even harmony of movement in a colony of 

 Volvox 5 or Eudorina. According to Migula the cilia of the cells of Gonium 

 do not work as harmoniously and regularly as those of Volvox. Inter- 

 protoplasmic communications occur between the cells of Volvox 6 , but have 

 not been detected in the case of Gonium^ and the existence of a dishar- 

 monic ciliary movement affords no proof of their absence. In ciliated 

 epithelium and in ciliated infusoria waves of action run over the cells or 

 body, each cilium bending over a little later than the one behind it, but 

 all retaining the same rhythm. The undulatory rhythm is maintained 

 by non-nucleated fragments of Infusoria, so that the regulation is due to 

 the ectoplasm 7 . 



1 Pfeffer, Unters. a. d^bot.^Inst. zu Tubingen, 1884, Bd. I, p. 391. 



a On the formation of cilia cf. Zimmermann, Beihefte z. bot. Centralbl., 1894, Bd. iv, p. 169 ; 

 A. Fischer, Jahrb. f. wiss. Bot., 1894, Bd. xxvi, p. 207; 1895, Bd. xxvn, pp. 34, 126; Strasburger, 

 Histologische Beitrage, 1900, Heft 6, p. 188; Jahrb. f. wiss. Bot., 1901, Bd. xxxvi, p. 520; Plenge, 

 Verhandl. d. naturh.-med. Vereins in Heidelberg, 1899, N. F., Bd. vi, p. 218; R. Hertwig, Archiv 

 f. Protistenkunde, 1902, Bd. I, p. 22 ; Maier, Archiv f. Protistenkunde, 1903, Bd. II, p. 73. 



3 For instances see Strasburger, 1901, I.e., p. 521. According to Rothert (Ber. d. bot. Ges., 

 1894, p. 277), the zoospores of Saprolegnia retract their cilia at the end of the first swarm-stage, but 

 not at the close of the second period of activity. On pseudopodia cf. Plenge, 1. c. ; Hertwig, Zelle 

 u. Gewebe, 1893, pp. 26, &c. ; Verworn, Allgem. Physiologic, 1901, 3. Aufl., p. 248. On the 

 pseudopodia of Amoeba radiosa, which vibrate like cilia, cf. Butschli, 1. c., p. 856. 



* See A. Fischer, 1895, 1. c., p. 73 ; Plenge, 1. c., p. 261. On Infusoria cf. Verworn, Psycho- 

 physiol. Protistenstudien, 1889, p. 169; A. Fischer, I.e.; Jennings and Jamieson, Biological Bulletin, 

 i902,*Vol. ill, p. 225. 



9 On Volvox cf. Klein, Jahrb. f. wiss. Bot., 1889, Bd. XX, p. 162 ; Migula, Bot. Centralbl., 1890, 

 Bd. XLIV, p. 104. . 



6 Kohl, Beihefte z. bot. Centralbl., 1902, Bd. xu, p. 345; Klein, 1. c. ; Migula, I.e.; Goebel, 

 Organography, 1900, Vol. I, p. 28. 



T Verworn, Psycho-physiol. Protistenstudien, 1889, p. 183. On ciliate epithelium cf. also Engel- 

 mann'in Hermann's Handbuch d. Physiologic, 1879, Bd. I, p. 385. 



