N. H. SWELLENGREBEL AND R. M. M. WiNOTO *271 
surrounded by a clear halo and so resembling small nuclei. The cyst 
now contains a vacuole, 4 large and 1-2 smaller nuclei or 5 nuclei of 
the same dimension (figs. 22, 23, 25). The cyst wall is especially 
distinct in cysts showing shrinkage (fig. 25). The vacuolate cysts 
measure 5-6 p,. 
The final stage of encystment is represented by the 4-nucleate cysts 
without vacuole (figs. 26-32), formed by the gradual disappearance 
of the vacuole (figs. 23-26).* The cytoplasm has a minute alveolar 
structure, the cyst wall only shows after shrinkage (fig. 28). Commonly 
these cysts contain 4 small nuclei (figs. 28, 29-32), sometimes the karyo- 
somes are larger and of granular structure (figs. 27, 31). Often smaller 
additional nuclei are found corresponding to the same formations in 
the vacuolate cysts (fig. 30). Finally these additional nuclei disappear, 
but before doing so they often exhibit signs of division (figs. 31, 32). 
It would be an easy task to construct a series from these figures 
showing a complete autogamy:—fig. 19, initial stage of encystment; 
fig. 20, first nuclear division; fig. 22, 5-nucleate stage; fig. 21, three 
nuclei (reduction nuclei) degenerate, two of them having divided 
beforehand, the remaining two (sexual nuclei) about to copulate; 
fig. 18, fusion of the sexual nuclei, formation of the synkaryon; fig. 24, 
first division of synkaryon; fig. 29, second division of the same; fig. 30- 
32, further division of reduction nuclei before disappearing.—But we 
prefer simply to state that the cysts initially containing a glycogen 
vacuole become afterwards avacuolate and that the uninucleate 
amoeba ultimately produces a 4-nucleate cyst with a 5- or 6-nucleate 
intermediate stage; some of the nuclei (probably the small ones, judging 
by fig. 30) must disappear. Undoubtedly this interpretation is not 
so interesting as that including the autogamy, but we think it the 
best, even if it should be proved afterwards that autogamy really 
occui% in this species. We do not want to follow the custom adopted 
by some authors of describing as reduction nuclei all sorts of chromatic 
granules observed during a process of encystment (in which the nuclear 
changes are somewhat intricate) and we are disinclined to consider 
the whole process as an example of autogamy. 
The 4-nucleate cysts containing no vacuoles are somewhat larger 
than the vacuolate cysts (6-6-5 p,). This difference probably depends 
upon the latter being more liable to shrinkage during fixation (the 
vacuole containing much w-ater) than the former. 
Forms were frequently noted (fig. 33), resembling 4-nucleate cysts 
but being much larger (8 p) and without a trace of a cyst wall. Possibly 
