THE MOVEMENTS AND REACTIONS OF AMCEBA. 135 



Umax contains usually a large number of fine granules, which in many 

 cases extend to the very outer surface, so that it is not possible to dis- 

 tinguish an ectosarc, in the sense of a layer containing no granules. 

 By watching the movements of these particles it is possible to determine 

 the direction of the currents in the protoplasm. The movements in 

 locomotion are usually as follows : At the anterior end there pushes 

 forth from the interior a clear substance, which I will call the 

 hyaloplasm. As this moves forward it spreads out laterally, till it 

 reaches a position such that it forms a continuation forward of the 

 remainder of the lateral boundary of the animal. Into this hyaloplasm 

 flows then the granular endosarc. The granules flow forward, rapidly 

 in the middle, usually more slowly near the sides. As it reaches the 

 anterior end the central current spreads out in a fanlike manner, so 

 that some of the granules approach closely the lateral borders of the 

 Amoeba (Fig. 35). They then stop, while the central part of the cur- 

 rent passes on, following the advancing anterior end. 



So long as one confines his attention to the Amoeba alone, not 

 observing external objects, 

 one receives the impres- 

 sion that there are two 

 sets of currents, an axial 

 current forward, marginal 



currents backward. But 



- FIG. 35.* 



as soon as one fixes his 



eye upon a particular granule in the apparent backward marginal 

 current, and observes its relation to some external object, he dis- 

 covers that no such current exists. The granule remains quiet, 

 retaining continually its position with relation both to other granules 

 in the edge of the Amoeba and to objects external to the Amoeba. 

 Meanwhile the remainder of the substance of the Amoeba is flowing 

 past, so that the granule in question after a time comes to occupy 

 a position at the middle of the length of the Amoeba. At about 

 this point it usually begins to move slowly forward again, though 

 much less rapidly than the internal current. The nature of this 

 slow forward movement we shall take up later (p. 166). The main 

 portion of the body of the Amoeba thus continues to pass the granule, 

 and the latter finally reaches the posterior end. Here it usually re- 

 mains quiet for a time (moving forward only as the posterior end is 

 dragged forward). Then it is taken into the central current again, 

 passes to the anterior end, and comes to rest as before, while the 

 remainder of the Amoeba passes it by ; and this process is repeated 



* FIG. 35. Diagram of the movements of particles in an advancing Amoeba. 

 Each broken line represents the path of a particular particle. 



