386 WM. A. KEPNER AND J. GRAHAM EDWARDS 



'eral type of stimuli, the Pelomyxa reacts to meet the con- 

 tingency of the possible escape of such ciliates and flagellates 

 as set up perceptible currents in the surrounding water. 



When the motile prey lies in the same plane as that in which 

 the Pelomyxa is moving we have observed the following ex- 

 amples of reaction. 



October 21, 1916. This day's observations were based upon 

 an individual that resulted when one Pelomyxa had been cut 

 into four parts. It was observed in a hanging drop of spring 

 water in which it had been since October 19 when the original 

 Pelomyxa had been divided into four pieces. It was noticed 

 that a Chilomonas had made a contact at a point indicated by 

 position 1 in figure 5. Two pseudopods were thrown out almost 

 at right angles to the direction of locomotion (indicated by the 

 arrow). One pseudopod was anterior to the quiet Chilomonas, 

 the other was posterior to it (a and a', fig. 5). An arching film 

 of protoplasm appeared as these pseudopods a and a' grew and 

 curved about the prey. Thus the prey was being surrounded 

 laterally and above and left with only one path of retreat be- 

 tween the advancing tips of the pseudopods and the margin 

 of arching protoplasmic film; the surface film of the hanging 

 drop of water prevented its escape from below. Pseudopods 

 a and a' advanced, their ends met and then bent in upon them- 

 selves as indicated by the dotted contours of their small tips; 

 next, the roof of the ^Chilomonas's enclosure was completed by 

 the advancing protoplasmic film fusing completely with the 

 inner margins of the two pseudopods. It was only when the 

 enclosure had been completed that the Chilomonas was dis- 

 turbed and began to dart excitedly about to and fro within the 

 gradually reducing enclosed space. As all these phases of the 

 reaction ran their course the main part of the body was flowing 

 by the part involved in the ingestion of the prey; so that by 

 the time the Chilomonas lay quieted within a vacuole of the 

 usual size the involved mass of Pelomyxa body lay well at the 

 posterior end of the body proper (fig. 5, 2). 



October 21, 1916. This observation was also made upon 

 one of the four parts into which a Pelomyxa had been cut on 



