STUDIES UPOX AMOEBA 
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contact with the pellicle (fig. 3). Soon the granules that lay be- 
tween vacuole and pellicle are pressed aside and the contour of the 
vacuole and the pellicle come to co-incide (figs. 4, 17 and 18). 
After usually some minutes of increasing pressure upon the pel- 
Hcle and of increasing protuberance, the pellicle finally breaks 
to form a minute pore^ and the contents of the vacuole exude so 
slowly that one has time to watch the change of form of the vacuole 
during its collapse (figs. 4, o, 6 and 7). In two instances I was 
fortunate enough to see particles in the water outside the Amoeba 
pushed away by the current from the collapsing vacuole. Their 
movement began slowly and was not at any time a very violent 
one, indicating that the jet thrown out from the contractile vac- 
uole is itself not ver>' violent. In one of the two instances a slight 
vortex was produced by the jet from the vacuole. 
Usually the very end of the contraction of the vacuole is slow. 
Very rarely a little of the contents of the vacuole may remain 
within the body and take part in the formation of the new vacuole. 
After the contraction of the vacuole and its disappearance, its 
former position is, as already described, very clearly marked 
by the presence of the mass of granules which formerly enveloped 
the vacuole (fig. 7). Soon the ectosarc between these granules 
and the pellicle becomes as thick as in other regions of the body 
and one sees that the mass of granules lies in the endosarc but 
touching the inner portion of the ectosarc (figs. 7-12). The ex- 
cretory vacuole of Amoeba proteus and probably of other species 
of Amoeba lies in the endosarc.^ 
Diastole takes place as has been described by others for Amoeba 
(figs. 7-19) . From one to three small vacuoles first appear (fig. 8) ; 
two of these may unite, forming a larger vacuole (fig. 9) ; new 
small ones keep appearing in the immediate neighborhood (figs. 
^ The pore is not itself visible, or at least I have not been fortunate enough to 
see it, but the manner of the collapse of the vacuole indicates a small opening. 
* It is customary in Amoeba to designate as ectosarc only the outer clear zone. 
The contractile vacuole does not lie in this zone. It does however lie in a less 
actively streaming zone attached to the inner surface of the clear zone. Doubtless 
the whole comparatively inactive outer zone, both its clear and its granular por- 
tions, is homologous with the ectosarc of ciliata. 
