230 THE BEHAVIOR OF LOWER ORGANISMS. 



prey. But, possibly, this trace was merely of a gross physical char- 

 acter, acting as a direct stimulus to produce the observed behavior. If 

 this is true, the behavior shows no indication of memory. 



SUMMARY. 



OBSERVATIONS. 

 THE USUAL MOVEMENTS. 



(1) Locomotion in Amoeba is a process that may be compared with 

 rolling, the upper and lower surfaces continually interchanging posi- 

 tions. This is shown by observation of the movements of particles 

 attached to the outer surface or embedded in the ectosarc of the animal. 

 Such attached particles move forward on the upper surface and over 

 the anterior edge, remain quiet on the under surface till the body of the 

 Amoeba has passed, then pass upward at the posterior end and forward 

 on the upper surface again. Single particles may thus be observed to 

 make many complete revolutions. (See p. 1 70, Fig. 58, and Figs. 38, 39, 

 40, 41.) * 



(2) Thus the upper surface moves forward in the same direction as 

 the internal currents, while the lower surface is at rest. There is char- 

 acteristically no backward current anywhere in Amoeba, though at 

 times some of the endoplasmic particles, spreading out laterally at the 

 anterior end, may move a slight distance backward at the sides. This 

 is rare (see p. 134). The forward current on the upper surface is not 

 confined to a thin layer, but extends inward to the endosarc ; the endo- 

 sarcal and surface currents are one (p. 142). 



(3) In the formation of pseudopodia that are in contact with the 

 substratum the movement of protoplasm is identical with that at the 

 anterior end of the Amoeba. The upper surface and internal contents 

 flow toward the tip, while the surface in contact with the substratum is 

 quiet. Particles adhering to the upper surface are carried out to the tip 

 and rolled under to the lower surface, where they remain quiet (p. 152). 



(4) In the formation of pseudopodia projecting freely into the water, 

 the movements of substance are the same as in pseudopodia that are in 

 contact, save that there is no part of the surface at rest. The whole 



* Of anyone who is inclined to reject these results on the basis of previous 

 observations, or of their supposed incompatibility with other known facts, let 

 me make the following request: Before taking ground against the results, pro- 

 cure some specimens of Amceba verrucosa or one of its relatives. This is usually 

 easily done. Then mix thoroughly with the water containing them some fine 

 soot, and observe carefully the movements of the animals. The particles attach 

 themselves to the outside, and the movements of the surface are then observable 

 with the greatest ease. It is such a simple matter to determine certain of the 

 chief points for one's self in this manner that it would be regrettable for contro- 

 versy to arise through neglect of the needed observations. 



