400 WM. A. KEPNER AND W. CARL WHITLOCK 
ther the small desmids nor the encysted Chlamydomonas rolled 
before the advance of the ameba, and they too were ingested 
within a closely fitting food vacuole. The observation, based 
upon the ingestion of an encysted Chlamydomonas, makes an 
interesting contrast with Jennings's ('04) observation of an 
ameba ingesting an encysted Euglena. In the latter case the 
encysted alga rolled ahead of the advance of the ameba, and 
here Jennings saw a cup form behind the algal cysts. This con- 
trast between our observation and that of Jennings suggests that 
even the type of reaction involved in ingesting non-motile objects 
may be modified to meet an unusual turn of events. There are 
some non-motile food objects which give off carbon dioxide. Of 
these, bacterial gleas form common examples. February 16, 
1918, Dr. R. D. Mackay observed an ameba glide over a glea. 
As it was about to leave the glea, two embracing pseudopods 
were sent out about the bacterial mass. These pseudopods lay 
close up to the sides of the rounded mass and eventually con- 
stricted a small portion from the glea as the enclosing pseudopods 
began to converge (fig. 4, a and b). 
In the above reactions we have the ameba responding to non- 
motile objects that gave off either oxygen or carbon dioxide. In 
reacting to this class of food, the amebas seized the objects in an 
intimate embrace. 
The following constitute a list of motile objects to which Ameba 
proteus has been seen reacting: a) Euglena viridis, Peridinium, 
and diatoms; b) rotifers, Paramecium caudatum, Urocentrum, 
Glaucoma scintillans, Colpidium, and two species of unidentified 
ciliates, Chilomonas, Codosiga, Euglena acus, and two species 
of unidentified flagellates. Of this group of motile food objects, 
a) forms a subdivision of forms that give off oxygen, while b) 
forms a subdivision of forms that yield carbon dioxide to the 
surrounding medium. 
The reaction of ameba to diatoms has been rather indefinite. 
The ameba seems to react to these motile plants as if they were 
non-motile. We have, however, obtained but two observations 
based upon diatoms, and in both of these cases the diatoms, 
while they were being intimately embraced, escaped. 
