FOOD-REACTIONS OF PELOMYXA 385 



erted enough pressure to cause one of the large ciliates to leave 

 the glcea and swim beneath the body of Pelomyxa as indicated 

 by the line 4. At 4-a it had escaped and a curtain of proto- 

 plasm was thrown above it, driving it back beneath the body 

 proper of Pelomyxa, from which it finally escaped along the 

 path leading to the head-end of line 4. In the meantime 

 pseudopods V and 3 advanced around the sides and over the 

 bacterial glcea causing it to be stretched into a bi-lobed mass, 

 the smaller lobe being squeezed out of the constricting region 

 between the bases of the pseudopods. This smaller mass, con- 

 taining two of the larger and nine of the smaller ciliates was 

 eventually, completely constricted and rejected. The larger 

 mass of the glcea was for the most part ingested by the means of . 

 the pseudopods 5 and 5' (fig. 4) encircling about it as indicated 

 by the contours 6 and 6'. As the tips of 6 and 6' approached 

 and fused, a minute mass of glcea containing one large and two 

 small ciliates was constricted. Two portions of the original 

 ciliate-containing glcea were thus at 11.20 a.m. rejected and the 

 third and largest mass was ingested. After this largest mass 

 had been ingested it was broken into small spheroidal masses, 

 each of which was now contained in a separate food vacuole. 

 At 12.15 p.m. the animal was just leaving the two rejected balls 

 of bacterial glcea and showed many food vacuoles within which 

 were active ciliates. 



Thus, in this type or reaction — reactions in response to non- 

 motile objects of prey — there is always an intimate embrace 

 of the prey whether oxygen or carbon dioxide be the chief factor 

 in setting up the stimulation as shown by the above examples. 



B. Reactions to objecis capable of retreat 



Such is not the case when Pelomyxa is reacting to motile 

 objects of prey. Flagellates and ciliates, even though they are 

 not at the time moving from place to place, are reacted to by 

 Pelomyxa in a definite way. A stationary Chilomonas, for 

 example, by the lashing of its flagella gives rise to currents in 

 the water which become a factor in the stimulus that acts upon 

 Pelomyxa. The following examples indicate how to this gen- 



