206 Proceedings of the Royal Physical Society. 
undigested food material, before the final encystment, and this adds to the 
débris already gathered from the surrounding water. 
Nestling then in this mass of débris so collected and ejected, the amoeba 
appears in transmitted light as a silvery grey mass, irregular in outline, 
with its protective wall as described; the irregularity soon disappears, and 
the form of the outer covering as well as the internal contents become 
spherical (Pl. VII. Fig. 1). At first, if such a mass be teased slightly with a 
needle, the amoeba will creep out and slowly attempt to push out blunt 
pseudopodia—but will make every effort possible, in its heavy condition, to 
return to the débris. If, however, the spherical form is well established 
then a push with the needle will send the whole cyst, as it can now be 
called, rolling out from the débris, and its individual form can be well seen. 
To obtain the amoeba, a careful tear can be made in the outer envelope 
by means of two needles, then a little gentle pressure on the wall opposite 
to the opening made will cause the now spherical amoeba to roll out. 
Only in one or two cases has the creature been seen, when this stage has 
been reached, to make any attempt to assume its own free irregular form 
or to put out pseudopodia. If so turned out, the amoeba remains inactive 
and degenerates. 
No rotating movement, as described by Scheel, has been seen during the 
encystment of the amoeba, but several times a ciliate has been observed to 
enter into a temporary cyst and show rotation within it after a manner 
answering to his description, the cilia working rapidly the whole time. It is 
a very deceptive process, especially as the ciliate is normally filled with 
refractive bodies—probably reserve food material. 
This ciliate will remain some time in the temporarily encysted condition, 
but a little irritation soon causes it to return to. its original form and swim 
through the water again. As, however, the organism never covers itself with 
débris for this purpose, the absence of such débris is a good criterion by which 
to judge whether a given cyst belongs to the ciliate. 
There is danger of confusion, however, with a temporarily encysted rotifer, 
which does so cover itself, and moreover produces a cyst in shape and size 
identical with the cyst of A. proteus, so that much trouble and sometimes not 
a little difficulty in distinguishing the two arises. This difficulty increases 
as the amoeba cyst ripens, since it then becomes as transparent as that of 
the rotifer. This in life; when fixed and stained in eosin, preparatory to 
sectioning, it also seems impossible to distinguish the cysts; but when they 
are sectioned the difficulty naturally disappears. 
Some attempts made by A. proteus to encyst without the protection of 
débris have been observed, but they were not a complete success; hence the 
