78 AMEBOID MOVEMENT 



tends from the outer surface to the endosarc; in other words 

 that the outer surface moves in continuity with the internal 

 substance (p. 150). 



"There is no regular transformation of endosarc into ectosarc 

 at the anterior end. On the contrary the ectosarc here retains its 

 continuity unbroken, moving across the anterior end in the same 

 manner as across other parts of the body. In the same way the 

 ectosarc is not regularly transformed into endosarc in the hinder 

 part of the body . . . Such transformation is by no means a 

 regular accompaniment of locomotion" (p. 174). 



According to Jennings, locomotion is aided by the projection 

 of waves of hyaloplasm at the anterior edge, "an active move- 

 ment of the protoplasm of a sort which has not been physically 

 explained." These waves, attaching themselves to the substratum, 

 enable the ameba to pull itself along by a rolling movement as 

 described in the quotation above. 



As to the rate of movement of the outer surface as compared 

 with that of the endoplasm, Jennings concluded : 



"The direction of movement of particles on the outer surface 

 is the same as that of the underlying particles of endosarc. The 

 rate is also about the same as for the endosarc, though often, or 

 perhaps usually, the outer particles move a little more slowly 

 than those in the endosarc" (p. 142). 



In view of the observations recorded in the preceding pages it 

 is clear that Jennings' statement that substance after moving 

 forward on the upper surface, rolls over the anterior edge is 

 quite erroneous. The attached particles, if heavy, may do so, but 

 the surface film itself does not. It is, on the contrary, taken into 

 the interior at the anterior edge. 



The statement that the movement of the outer surface is con- 

 gruent with that of the ectoplasm can likewise not be substantiated 

 by observation, as has been demonstrated in the preceding pages. 

 It is difficult to distinguish between the ectoplasm and the surface 

 layer in such amebas as sphaeronucleosus and vernwosa, for there 

 are no large crystals or other bodies which get caught in the 

 ectoplasm as it is formed from endoplasm at the anterior end. 

 But attentive observation will demonstrate very definitely that the 

 ectoplasm here is stationary to the same degree as in proteus. 



