The Cyst of Amoeba proteus. 205 
during which encystment naturally takes place appear to be January and 
February, subject no doubt to fluctuations from late December to the 
middle of March, according to the severity of the winter, although from 
experiments tried it would seem that cold is not by any means the most 
important factor in the process of encystment. 
APPEARANCE OF CYST. 
All that Scheel said of the external appearance of the amoeban cyst 
upon which he worked may also be said of the one here described. 
The cyst is spherical in form, and has no means or method of attachment. 
Its outer surface is covered so completely with plant detritus, diatoms, etc., 
that in life only the outline of the internal contents can be seen ; occasionally, 
however, if the débris is of a light character, the granular protoplasm and 
the nucleus can just be discerned in the early cyst. Scheel mentions this 
outer covering, but does not show it in any of his drawings. In transmitted 
light the amoeba-body shines as a silvery mass through the “glassy zone” 
and rough débris. 
In no case has a group of cysts been found, as figured by Scheel, in 
one enveloping outer wall. The cysts do occasionally cling together by 
their outer coating of débris, but this in no way interferes with their 
individual constitution. 
ENCYSTMENT OF THE AMOEBA. 
When about to encyst, the amoeba, which at this time is usually very 
well fed with diatoms and other organisms, becomes heavy in appearance 
and sluggish in its movements. A slimy mucous substance is exuded by 
the slowly moving creature which causes the diatoms, other small organisms 
and plant remains occurring in its path to adhere to the outer surface of 
the protoplasm. In fact this exudation, whatever it may be, makes the 
touching of the amoeba at this time a very difficult task. When the animal 
is in its normal condition, it is quite an easy matter to move it about by 
means of a seeker or fine blunt needle, without the least risk of injury ; 
but when the slime is covering the surface, a seeker placed on the amoeba 
is soon smeared with the exudation, and the protoplasm of the specimen 
touched clings to it in such a way as to cause the disruption, if not the 
death, of the creature when an attempt is made to withdraw the 
instrument, 
The amoeba casts off all waste products, such as diatom-shells and 
