406 WM. A. KEPNER AND W. CARL WHITLOCK 
vacuole, the prey being in the smaller vacuole. The Chilo- 
monas was not disturbed until it was thus enclosed within the 
smaller vacuole. The filament of Oscillatoria was further in- 
gested, but it was finally rejected. Thus, while a reaction to a 
non-motile object was being carried on, the ameba completed a 
food reaction of the second type, in capturing a passive motile 
object. 
Chilomonases have been seen to swim in beneath unattached 
regions of amebas' bodies. In such cases, when the amebas react 
positively to the flagellates, a curtain of cytoplasm is dropped 
down around the prey, the lips of which turn in beneath the food 
body and fuse without disturbing the Chilomonas. 
Perhaps the most interesting reaction we have seen was that 
of an ameba reacting to a Chilomonas that had come to lie against 
the tip of a pseudopod (fig. 21, 1). The ameba sent out two 
pseudopods in response to the stimulus. The smaller pseudopod 
arose from the side of the parent pseudopod and a httle behind 
its end, while the larger secondary pseudopod came out quite a 
distance behind the tip of the parent one. The interesting fea- 
ture of this reaction is the fact that the parts reacting to the 
source of stimulation are parts least stimulated; indeed, the 
greater reaction was displayed by the least stimulated part. The 
quiet Chilomonas could stimulate the parent pseudopod in two 
ways : either chemically by means of its metabolic by-products, 
or physically by means of shght vortices that the play of its 
flagella may set up. In either case the end and not the sides of 
the parent pseudopod would be most affected by these stimuli. 
Moreover, we have studied the types of vortices set up in the 
water by quiet Chilomonases. This study showed that in aU 
cases the strength of the currents thus set up was greatest at the 
anterior end of the Chilomonas. Finally, as the two secondary 
pseudopods were coming out by the sides of the Chilomonas, a 
second Chilomonas came to lie at position 2, figure 21, and thus 
double, or at least increase, the sources of stimulation; but this 
did not modify the conduct of the two secondary pseudopods. 
These facts indicate that the ameba's reaction is a qualitative 
and not a quantitative one. 
