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Amoebae 
(1) Amoeba of type (a). 
Ill this way cultures of Amoebae were obtained which were found 
to form cysts of type (a) only. If such a culture be allowed to encyst, 
the cysts be transferred to a slide preparation, as above described, and 
one of them be isolated under the 1/12th immersion-lens, its develop¬ 
ment may be followed in detail. 
After 1-3 hours (at a temperature of 22°-28° C.) a faint streaming 
movement of the contained granules becomes evident and a bright 
vacuole appears in the plasma. After a very variable period—from 
10-35 min.—the vacuole suddenly shuts and either disappears en¬ 
tirely or leaves only a minute dark speck to inark its site; then, 
very slowly and gradually, it reappears. This process is repeated 
at diminishing intervals until the vacuole may contract after irregular 
periods of 40-180 seconds, the streaming of the granules becoming more 
and more active and the nucleus more clearly apparent in the meantime. 
After 3-7 hours, as a rule, from the time of insemination, during active 
movements of the contents, a small knob of protoplasm is seen to thrust 
suddenly through the cyst wall at one point (PL VI, fig. 2). Streaming 
through the narrow outlet, the active amoeba rapidly increases in size, 
so that a considerable portion of it may escape without any coincident 
shrinking of the contained part away from the inner wall of the cyst. 
The amoeba may become completely clear of the cyst within 5-20 
minutes of the rupture, and may, by that time, have reached a diameter 
of 15-25 fjb. 
The nucleus stands out distinctly as a circular or oval body with 
a dark centre and a clear peripheral halo; the total diameter is about 
2‘5 jx. One contractile vacuole is invariably present-which, at this stage, 
generally contracts, somewhat in’egularly, once in 20-80 seconds and 
there may, more rarely, be two or more; clear circular areas, about 
1-2 y in diameter, which remain uncontracted are often seen in the 
plasma (PI. VI, fig. 5). Sometimes the distinction between ectoplasm and 
endoplasm is remarkably clear but often the protoplasm is uniformly 
granular. In this respect the same amoeba shows varying characters 
at different times. The vary much in form, may be broad 
and blunt or spinous, simple or branched; the commonest form seems 
to be a single, rather broad or blunt process, the margin of which is 
fririged with short spikelets. Several pseudopodia may be protruded 
in different directions at the same time; many bacteria may be in- 
