306 
MAYNARD M. METCALF 
quently and at irregular intervals, and in its contraction many of 
the contained granules are thrown out and may afterward be found 
for a considerable time stuck to the posterior cilia of the Opalina. 
These granules seem to be connected functionally with excretion. 
The somewhat similar granules in Amoeba, if engaged in excre- 
tion (as seems to me altogether probable), are apparently less 
speciaHzed than those in Opalina, for they show no special stain- 
ing reactions differentiating them from the ordinary cytomicro- 
somes. 
My colleague. Prof. Biadington, has experimented with these 
same Amoebae, and he kindly allows me to incorporate here 
reference to some of his results of interest in connection with my 
observations. He found, when part of the body of an Amoeba is 
cut off and wich it the contractile vacuole and its mass of granules, 
that the other portion of the Amoeba remains for a considerable 
time without a contractile vacuole, but later forms one. At first 
the new vacuole has few granules around it. The granules in- 
crease in number until (as I found), after about three hours, there 
are around the vacuole about one- third asmanygranules as around 
an ordinary vacuole. Probably in time the full number of gran- 
ules would collect, but no individual has been observed long 
enough to prove this. The new vacuole will form in the divided 
Amoeba either when the nucleus is present or when it is absent, 
and it forms about as quickly in one case as in the other. The 
behavior of the new vacuoles formed in such divided Amoebae 
is the same as in normal Amoebae. 
From these observations of Prof. Budington's it is evident that 
more than one portion, probably any portion, of the outer la3^er 
of the endosarc of an Amoeba may form a contractile ^^acuole, 
but it is also evident that when a contractile vacuole is once formed 
it soon associates with itself a mass of granules, and that this 
association persists, and that no portion of the protoplasm will 
ordinarily, if ever, form a new contractile vacuole so long as the 
already collected mass of granules associated with the old vacuole 
persists. Apparently there is just the beginning of specialization 
of cytomicrosomes in connection with excretion, and when there 
is a mass of these slightly specialized granules present, others 
