118 
W. GLEN LISTON AND C. H. MARTIN. 
It is apparent that when conditions are unsuitable for the 
growth of the amoeba, a single individual by condensation 
of its protoplasm and the development of a cyst-wall becomes 
encysted, and, when the conditions are favourable, a single 
amoeba escapes from this cyst. No evidence of conjugation 
was observed before encystment and no multiplication or 
division of the nucleus noticed, either immediately before or 
after encystment. Encystation appeared to be a purely 
protective measure. Outside the body the amoeba was 
able to feed and to multiply under favourable circumstances, 
but it encysted when circumstances were unfavourable for 
development. 
I will pass on now to describe some experiments which 
were made with a view to finding- out whether the large 
amoeba of the liver-abscess culture could absorb food osmoti- 
cally and live and multiply on the agar medium in the absence 
of bacteria. 
Much time was spent in the first instance in attempting to 
get the amoebae from the four sources mentioned above to 
grow with a single species of bacteria. This was compara- 
tively easily accomplished with the large amoeba from theliver- 
abscess culture, but with greater difficulty in the case of the 
other amoebae. All the “ pure mixed ” cultures were ultimately 
obtained with motile organisms except in the case of the 
large amoeba from the liver-abscess. In this case the amoeba 
was cultivated with a variety of motile and non-motile 
organisms, but particularly with a non-motile, yellow, pigment- 
producing coccus. With this pure mixed culture a number of 
experiments were conducted, and these are detailed below. 
This amoeba with the non-motile coccus multiplied enor- 
mously on the agar medium. The young amoebae moved 
away from the immediate neighbourhood of the bacteria and 
ultimately became encysted. Using such a culture it was 
comparatively easy to separate amoeba cysts from bacteria. 
With these cysts free from bacteria a number of experiments 
were carried out. 
(1) A single cyst, free from bacteria, was isolated and 
