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MAYNARD M. METCALF 
10 and 15); from time to time these fuse with one another, or 
unite with the larger ones, till soon there are two or three moder- 
ate size vacuoles present (fig. 20) ; ultimately all fuse into one 
vacuole (fig. 16), which continues to enlarge until full size is 
reached (fig. 17), when it begins to push through the ectosarc 
as already described. 
All these small vacuoles which appear and fuse lie among the 
granules in the mass referred to, or just outside them. There is 
a perfectly definite and constant relation between this mass of 
granules and the excretory vacuoles. 
The Amoebae upon which these observations were made were 
for the most part very active. Their endosarc currents were 
very violent. It was often easy to see that the mass of granules 
surrounding the excretory vacuoles does not flow with the more 
rapid stream, but remains attached to the inner side of the more 
slowly moving ectosarc, and protrudes into the more rapid stream. 
This rapid stream tugs at the mass of granules, but in only one 
instance have I seen it produce any effect. Once the mass of 
granules was broken into two and the small group, surrounding 
a rather small vacuole, was carried off into the stream, while the 
rest of the granules, surrounding two moderate sized and two very 
small vacuoles, remained in position attached to the ectosarc. 
Unfortunately I followed the fate of the larger, more nearly sta- 
tionary group of granules and do not know what became of the 
smaller group that flowed away. Infrequently, among these 
Amoebae, individuals with two contractile vacuoles are seen. One 
naturally imagines that this condition with two vacuoles may be 
due to a division oi the mass of granules as just described, though 
I have not completely traced the origin of the second vacuole. 
The mass of excretory granules lies, as described, attached to the 
inner surface of the ectosarc and does not flow with the endosarc 
currents. It is easy to determine that this connection with a par- 
ticular region of the ectosarc is a constant one. The mass of 
excretory granules flows with the same rapidity as the adjacent 
ectosarc granules^ and it is plain that there is a constant associa- 
5 These are much less evident than the endosarc granules, but can be observed. 
