280 LOCOMOTORY AND PROTOPLASMIC MOVEMENTS 



of the protoplasm. The ectoplasm may not only include the somewhat 

 thinner layer of hyaloplasm, but also a little of the neighbouring layers 

 of granuloplasm. 



By using plasmodial threads of about 0-3 mm. in thickness, in which 

 the surface-tension effect is small, Pfeffer 1 was able to determine that 

 the consistency was about that of a jelly, and the same is shown by the 

 way in which moving particles are repelled from the surface layers without 

 producing any perceptible deformation or inducing any streaming move- 

 ment. Similarly oil-drops and vacuoles passing through a tube of 

 ectoplasm are compressed and distorted without producing any bulging 

 in the tube. The appearance closely resembles that shown when fluid 

 gelatine containing suspended particles is passed through a fine glass tube 

 kept lined with a layer of solidified gelatine 2 . The existence of such 

 a condition of cohesion in the peripheral layers renders it impossible 

 that amoeboid movement can be directly and solely due to a modification 

 of surface-tension. In addition, the increased surface involves an increase 

 of the total amount of ectoplasm, and this is probably the result of the 

 same vital activity which yields the energy for movement. It is, however, 

 uncertain whether the retraction of a pseudopodium is due to an active 

 change of shape or to a softening of the ectoplasm allowing surface-tension 

 to come into play. Possibly both factors may co-operate. The streaming 

 movement of the endoplasm is probably the direct result of the successive 

 contractions and expansions, the direction of movement being towards 

 the region of expansion. Hence but little endoplasm escapes when a 

 plasmodial thread is severed 3 , whereas when an internodal cell of Chara 

 is cut open a large quantity of the streaming endoplasm may escape 4 . 

 When the streaming is reversed in a thread the return movement begins 

 at the end nearest to where the expansion or contraction is most active 5 . 



It is always possible that the amoeboid movements of certain 

 organisms may be solely due to surface-tension 6 , although the arguments 

 of the different authors supporting this view are mainly based upon 

 the assumption that the whole of the protoplasm is fluid. In many 

 Amoebae, however, the temporary presence of a firm ectoplasm has been 



1 Pfeffer, Zur Kenntniss der Plasmahaut n. d. Vacuolen, 1890, p. 264. 



3 Id., p. 263. 



3 De Bary, Mycetozoen, 1864, p. 48. 



' See Cord, Meyen, Pflanzenphysiologie, 1838, Bd. II, p. 218. [The shock always causes 

 a temporary stoppage of streaming, and the phenomenon is only shown properly if streaming is 

 resumed again before death ensues, which is not always the case.] 



5 Cf. de Bary, I.e., p. 48 ; Biitschli, 1. c., p. 175. 



* Berthold, Protoplasmamechanik, 1886, p. 85 ; Biitschli, Unters. liber mikroskopische Schanme, 

 1892, p. 172; Verworn, Die Bewegungen der lebendigen Substanz, 1892, p. 36; Rhumbler, Archiv 

 f. Entwickelungsmechanik, 1898, Bd vm, p. 171; Zeitschr. f. allgem. Physiologic, 1902, Bd. I, 

 p. 279 ; 1903, Bd. II, p. 183 ; Jensen, Pfliiger's Archiv f. Physiologic, 1901, Bd LXXXVII, p. 361. 



