THE MOVEMENTS AND REACTIONS OF AMCEBA. 



133 



the Rhizopods by Penard (1902) contains incidentally a large number 

 of valuable observations on this matter. 



According to Rhumbler il. c.) the movements in normal locomotion 

 are typically as follows : From the hinder end of the Amoeba (or of the 

 pseudopodium, if a single pseudopodium is under consideration) a 

 current of endosarc passes forward in the middle axis ; in front this flows 

 outward toward the sides, then backward along the surface, gradually 

 coming to rest. Figs. 30 and 31 , taken from Rhumbler, give diagrams 

 of these currents in an Amoeba moving as a whole (Fig. 30), and in 

 the formation of pseudopodia (Fig. 31). In an Amoeba which forms 

 more than one pseudopodium at once, these typical currents become 

 somewhat complicated (Fig. 32), but retain their main features. The 

 backward current shown at the sides in Figs. 30-32 is conceived to be 

 present also above and below, that is, over the whole surface of the 

 Amoeba. A diagram of the currents in side view, as given by Rhum- 

 bler, is shown in Fig. 33, B. An essentially similar account of the 

 currents is given by Butschli (1880, 1892). 



Fig. 30.* 



Fig. 31. t 



Fig. 33.t 



Fig. 33-§ 



The most striking feature in the currents as above set forth is the fact 

 that they agree precisely with the currents produced in a drop of fluid 

 of any sort when the surface tension is lowered over a certain limited 

 area. There is always a current over the surface away from the region 

 where the tension is lowered, while an axial current moves toward the 



* Fig. 30. — Diagram of the currents in a progressing Avtccba Umax, after 

 Rhumbler (1S98). 



fFiG. 31. — Diagram of the " fountain currents " in pseudopodia of Amoeba, 

 after Rhumbler (189S). 



J Fig. 32. — Diagram of complex " fountain currents" in an Amoeba with two 

 large pseudopodia, after Rhumbler (1898). 



§ Fig. 33. — Comparative diagrams of the currents in a rolling movement, nnd 

 in the movement of Amceba, as conceived by Rhumbler, viewed from the side. 

 In A are represented what Rhumbler conceives to be the necessary currents in 

 a rolling movement, while B represents what Rhumbler considers the really 

 existing currents in Amoeba, as seen from the side. The heavier arrows in each 

 case represent the current on the lower surface. After Rhumbler (189S). 



