The Cyst of Amocba proteus. 209 
Attempts to stain intra-vitam produced little or no effect. The pores in 
the cyst walls mentioned by Scheel have not been observed. 
CONTENTS OF THE CYSTS AS SEEN IN SECTIONS. 
The outer envelope of débris, small stones, etc., shows up very well in 
the sections, always maintaining its spherical or oval form, while the inner 
membranous walls collapse as a rule. 
The tenacity of this outer envelope seems to confirm the idea that its 
constituents are cemented together by the slimy exudation already referred 
to. 
Thus the combined study of the process of encystment, as seen in life 
and in the sectioned cysts, leads one to conclude that after the cementing 
of the débris the amoeba-body withdraws itself from its protective envelope, 
and rounding itself off forms its outer membranous wall. After this a 
slight contraction of the protoplasm as it concentrates, and the formation 
of the second membranous wall, completes the protection of the now encysted 
amoeba. 
As the cyst ripens the membranous walls contract and crumple round 
about the amoeba-body, while, as mentioned earlier, the wall of débris remains 
intact until the young amoebe are ready to escape (PI. VII. Fig. 9). The 
period of encystment lasts from 10 to 12 weeks. 
THE NUCLEUS. 
The nucleus breaks down; the chromatin and plastin are distributed 
throughout the cytoplasm, and secondary nuclei are formed. These secondary 
nuclei are of the protokaryon type, showing a relatively large karyosome 
slung up in the nuclear sap by achromatic radiating fibres, each terminating 
in a chromatin granule similar in all appearance to the karyosome but 
retaining the stain less intensely (Fig. 9a). No membrane has been dis- 
tinguished at this stage. These secondary nuclei resemble that shown by 
Glaser! for A. tachypodia. Described on the alveolar theory the achromatic 
fibres become the lines of demarcation between the alveoli in the secondary 
nucleus, but the absence here of a membrane presents a little difficulty. 
THE DIFFERENTIATION OF THE YOUNG AMOEB. 
The nuclei now cut off portions of the cytoplasm forming the young 
amoebe—not in this case the numbers mentioned by Scheel, 500 to 
1 Glaser, “ A. tachypodia,” Archiv fiir Protistenkunde, Bd. 25, p. 27, 1912 
