310 
MAYNARD M. METCALF 
Stan; relation to any particular portion of the ectosarc. May- 
there not be a correlatioa between this fact and the fact that this 
vacuole rarely, if ever, contracts? In the Amoeba proteus de- 
scribed in Part I, the contractile vacuole gradually pushes outward 
through that portioQ of the ectosarc which especially belongs to 
it, until it reaches the pellicle. It causes ohis pellicle to bulge 
outward, until finally, after a number of minutes, this bit of 
stretched pellicle ruptures and allows the contents of the vacuole 
to exude. It requires considerable and continued pressure upon 
the ectosarc and pellicle to secure an aperture for the discharge 
of the contents of the vacuole. In the rapidly flowing parasitic 
Amoeba, we are now describing, no one region of ectosarc a id pel- 
licle remains long enough in contact with the vacuole for the vac- 
uole to succeed in pressing its way through to the exterior. That 
there is pressure upon the nucleus and vacuole, urging them for- 
ward, is apparently shown by the fact that tha': face of the nu- 
cleus and 'hat face of the vacuole which touch one another are 
both slightly flattened as if from pressure. This pressure, caused 
doubtless by the forward currents of the endosarc, is insufficient 
to force the vacoule through the constantly changing portion of 
ectosarc and pellicle in froat of it. 
When I again have access to my notes upon this species I shall 
pubhsh a somewhat fuller description, giving measurements. T 
shall then name this species Amoeba (Entamoeba)^ currens be- 
cause of this very active locomotion, more rapid than in even the 
most active A. proteus or A. limax, and far more rapid than in 
Entamoeba coli or E. tetragena. 
^ I do not distinguish between Amoeba and Entamoeba, for I have found, in 
what I take to be minute Amoeba proteus, nuclei of exactly the Entamoeba type. 
The parasitic habit is not sufficient for generic distinction, and no more is the fact 
that some species of Amoeba have a vegetative stage when their bodies are very 
large and their nuclei do not show caryosomes and caryoles. 
