PROTOPLASMIC MOVEMENT. 415 



tion of processes in a manner corresponding to the older 

 conceptions, in Myxomycetes. But here, according to De Bary, 

 the protoplasm becomes contracted behind the streaming 

 region quite irregularly, the rapidity of the streaming dimin- 

 ishes towards the periphery. In a similar manner local, and 

 especially progressive, contractions of inotagma groups, local 

 differences of pressure, may be produced in the interior of the 

 protoplasm, and following thereupon occur streamings and 

 changes of relative position of those masses which are easily 

 moved. 



The theory put forward by Briicke^ for Urtica, that the 

 progressive movement of the protoplasmic contents (granules, 

 nuclei, vacuoles, &c.) always, or at all events generally, takes 

 place in a way analogous to that in which a fluid is moved 

 forward by the contractions of the enclosing pipe walls, is unten- 

 able after what we have said.- 



Note. — It is moreover clear that the formation of processes 

 and streamings may be brought about without physiological 

 contractions, by mere shrinking of the superficial layer (as in 

 partial drying, which for instance occurs not unfrequently in 

 very large plasmodia, or by the coagulation of the albumen, 

 e.g. after ultramaximal electrical excitations). Of course all 

 kinds of combinations of the different means of formation of 

 processes and streamings which have been described may occur 

 especially in experiments with artificial excitations. 



3. Rotation of the Protoplasm within firm Cell- 

 Walls. 



This must take place when the inotagmata of the moving 

 layers are distributed with their long axes parallel to the direc- 

 tion of the movement and a forward movement of the spon- 

 taneous stimulus takes place in this direction. The moving 



' Briicke, * Sitzsber, d. Wiener Akad. Mathetn. Naturw. CI.,' xlvi, 1863, 

 * Cp. also the refutation of the universal applicability of this view by M. 



Schultze, 'Das Protoplasma, &c,,' p. 51, et seq. ; also A. De Bary, " Ueber 



den Bau ii. das Wesen der Zelle," ' Flora,' 1862, p. 249. 



VOL, XXIV. NEW 8ER. F F 



