FOOD-REACTIONS OF AMEBA PROTEUS 399 
angles, and the ameba then gave up its efforts to lay hold of this 
food. Throughout all of the time that the ameba was working 
on this rather long filament of Oscillatoria it had within its body 
a filament of Oscillatoria that was 30m long when first seen. 
Within the course of our observation, this ingested filament was 
broken up into three pieces, one 10/x, one 5m, and one 15m. 
After we had secured several observations showing that the 
ameba laid hold of quiet Oscillatoria filaments tightly, we called 
in some of our colleagues in this laboratory to make observations. 
Six others verified our results by making similar observations. 
The most conspicuous of these corroborative records was made 
by Dr. I. F. Lewis. He was given an ameba that had ingested 
an end of a very long filament, indicated as broken off in figure 3. 
He took a fine glass rod and bent the plant to contour b (fig. 3), 
at which point the tension of the alga caused it to spring back as 
a straight rod. "Twenty big bends, some like this, others differ- 
ent, were made as the ameba gradually lost its hold." 
No such large filaments have been ingested wholly. The 
ameba sometimes travels from end to end along such long objects, 
sometimes making several trips, and then leaves the food behind. 
Frequently small fragments have been seen in different stages of 
digestion within amebas (fig. 5, 0). It would seem that the 
ameba seeks the planes of fission of the Oscillatoria filaments to 
break off fragments for food. Such may not be the case, how- 
ever, for we have seen an ameba travel along a Mougeotia fila- 
ment in a similar manner, and there are no fission planes in 
Mougeotia. No Mougeotia filaments or fragments were ever 
seen completely ingested. Large desmids were also ingested in 
part and then rejected. On one occasion, January 28, 1919, two 
amebas began to ingest opposite ends of a large Penium syn- 
chronously. The lower half of the desmid was ingested within 
twenty minutes by one of the amebas. During this period the 
upper ameba ingested about one-third of the desmid. Both 
amebas were closely embracing the plant, but they eventually 
rejected the object by withdrawing from it. Small desmids have 
been observed by us being ingested by Ameba proteus. A Chla- 
mydomonas within its gelatinous sheath was also ingested. Nei- 
