THE MOVEMENTS AND REACTIONS OF AMCEBA. 



137 



at variance with certain statements of F. E. Schulze, Biitschli, and 

 Rhumbler. I am aware that this conflict of my observations with 

 those of the investigators named, who deservedly rank among the 

 highest in the field at present under consideration as well as elsewhere, 

 renders the utmost caution necessary in trusting to these results. Yet, 

 with this consideration in mind, and with the confident expectation in 

 undertaking the work that I should find the currents exactly as described 

 by these authors, I have been unable to come to any result save that 

 above set forth. The statements of Schulze (1875, pp. 344-348) deal 

 with Pelomyxa palustris Greef. In this animal, according to Schulze, 

 there are resting portions at the sides of the body, while from behind 

 currents pass forward through the channel enclosed by these resting 

 portions. At the anterior end the lateral parts of these currents turn 

 outward and, finally, a little backward ; any 

 given portion passes backward but a short dis- 

 tance. The currents are shown by Schulze in 

 a figure, a reduced copy of which is given here- 

 with (Fig. 37). According to Schulze the cur- 

 rents have this form on the upper surface as well 

 as at the sides that is, a part of the current flows 

 upward and backward on the upper surface. 

 Biitschli (1892, Anhang, p. 220) confirms this 

 account of the currents in Pelomyxa. 



I regret that I have been unable to obtain 

 specimens of Pelomyxa in order to examine 

 these phenomena for myself. One would of 

 course be bold to doubt the correctness of the 

 observations of such investigators as Schulze 

 and Biitschli, and it is possible that Pelomyxa differs from Amoeba 

 in this respect. Yet, as we shall see later (p. 149), the account given 

 by these authors is certainly incorrect so far as the backward cur- 

 rents on the upper surface are concerned ; it is possible, then, that the 

 appearance of a backward current elsewhere was deceptive. 



Rhumbler (1898) describes the forward axial and the backward side 

 currents in various species of Amoeba, and considers such movements 

 as typical, basing his theory of locomotion upon them. It seems 

 probable that slight backward, currents, such as were described by 

 Schulze (Fig. 37) , do occur at times at the sides of the advancing 

 anterior end. The posterior part of the Amoeba is narrow and 

 rounded, the anterior part broad and thin. The current of endosarc 

 flows from this narrow posterior portion into the broad anterior part 



FIG. 37.* 



*Fio. 37. Currents in a progressing Pelomyxa, as seen from above, after 

 Schulze (1875). The longer arrows represent stronger currents. 



