PHYSIOLOaV OF CELLS Gl 



ment is muscular contraction. The first three types of protoplasmic 

 movement will be discussed here, the fourth in Chapter VII. 



Flowing of Protoplasm. — In many living cells the protoplasm may be 

 observed to be in process of circulation, particle following particle in a 

 more or less definite course within the cell boundary. Such a movement 

 involving not only protoplasm but also granules and food vacuoles which 

 are swept along by the current may be observed in Paramecium and some 

 other species of Protozoa. In many plant cells, as in Nitella, Chara, the 

 stamen hairs of Tradescantia, leaf hairs of the tomato, and cells of aquatic 

 plants like Elodea, a similar movement of protoplasm, sometimes in- 

 volving the chloroplasts, may be observed. When the movement of the 

 particles describes a definite closed circuit it is sometimes called cyclosis 

 or rotation. In some plants, as in sorrie of the fungi whose mycelia are 

 not divided by cell walls, the protoplasm moves toward one end of the 

 mycelium and then returns. This may be called streaming of protoplasm. 

 Flowing of protoplasm of the kind described does not result in 

 locomotion. 



Amoeboid movement. — When an amoeba moves it thrusts out one 

 or more lobe-like processes, called pseudo-podia. Then the body is pulled 



Fig. 26. — Diagram illustrating the movements of a particle of soot attached to the 

 outer surface of Amceha verrucosa, in side view. X marks the location of the soot particle 

 in position 4 of the amcEba. In position 5 the particle is still at X but the figure has been 

 raised a trifle in order to show the outline of the amceba. {From Jennings.) 



forward or flows forward. Since there seem to be two methods of locomo- 

 tion in Amoeba both will be described. Amceha verrucosa, an amoeba 

 with a very viscous outer laj'er or ectosarc, puts out normally a single 

 pseudopodium in contact with the substratum. The protoplasm of the 

 upper surface flows toward the tip of the pseudopodium, while the proto- 

 plasm of the lower portion flows to the rear, thence to the upper surface 

 and to the anterior end. Thus this amoeba acts like an elastic sac filled 

 with a viscous fluid. For an experiment in demonstration of this type 

 of amoeboid movement zoologists are indebted to Jennings who mixed 

 soot in water containing Amoeba and then traced the path of the soot 

 particles which adhered to the surface of the animals. Figure 26 illus- 

 trates Jennings's idea of locomotion in Aynceha verrucosa. In Amceba 

 proteus a number of pseudopodia may be thrust out. The anterior end 

 is elevated, thrust out, and then brought in contact with the substratum 

 with which it adheres. The posterior portion of the body is now brought 

 forward by contraction of the protoplasm and this material now forms 

 a new anterior end. Dellinger demonstrated this method of locomotion. 



