STUDIES UPON AMOEBA 
307 
will not take on the function and enter into rivalry with them. 
Amoeba seems thus to show real though very slight physiolog- 
ical differentiation on the part of certain cytomicrosomes in con- 
nection with excretion. Opalina shows a higher differentiation. 
What causes the granules to collect about the contractile vac- 
uole? The results of Prof. Budington's operations upon Amoeba 
show that a new vacuole in aa Amoeba fragment appears first 
and that only gradually the granules collect about it. The gran- 
ules are not essential to the functional vacuole. All the appear- 
ances seem to indicate that the excretory granules come from the 
ordinary cytomicrosomes and are but very slightly modified 
functionalh^ from the general cytomicrosomes. May it not well 
be that the repeated contraction and expansion of the vacuole, 
with the somewhat intermittent flow of liquid from the cyto- 
plasm to the vacuole, cause some of the cytomicrosomes to move 
with the currents toward the vacuole and thus to form the group 
of granules described? Of course all the cytomicrosomes, like 
all the nuclear and extra-nuclear protoplasm, are engaged in 
metabolism and share in excretion. Apparently the special group 
of granules around the vacuole is slightly modified functionally, 
else why should the presence of a contractile vacuole and its 
granules in one region of the body prevent the formation of 
other contractile vacuoles in other regions of the body, since Prof. 
Budington's operations show that probably any region of the 
body is capable of forming a contractile vacuole. 
I have not as yet had favorable material for studying these 
phenomena in other species of Amoeba. Tlie species I had for 
study seems to be a form of Amoeba proteus. The individuals 
were very large and quite typical Amoeba proteus, except that 
their diet was almost exclusively bacteria, which is not ordinarily 
true of Amoeba proteus, and excepting also the condition of the 
excretory granules which are not so clearly marked in most Amoebae 
of this species. 
