4 
INTllOBUCTION. 
be distinguished from the rest of the hyaline element, and 
appear to contain refuse matter. After a time the creeping 
movement is again exchanged for the dancing. In all cultivations 
of germinating spores, a number of the swarm-cells, after a short 
period of activity, withdraw the flagellum and become encysted 
in a globular foi-m, as the microcysts of Oienkowski. After being 
dried and re- wetted, the contents iDursts the membranous cyst-wall, 
which remains as an empty hyahne sac, and emerges to resume 
the swarm-cell form. If bacteria are introduced irito a cultivation 
of swarm-cells on the stage of the microscope, they are seen to 
be laid hold of by the pseudopodia and drawn into the body of 
the swarm-cells, where they are enclosed in a digestive vacuole. 
Several bacteria are brought in turn to the same chamber, or fresh 
captures are conveyed into one or more additional vacuoles. The 
protrusion of pseudopodia usually ceases after such ingestion, and. 
that part of the swarm-ceil 
takes a rounded form. In 
the course of an hour or two 
the bacteria are assimilated, 
and the digestive vacuoles dis- 
appear. Unicellular algae and 
inorganic matterare sometimes 
taken in, which after a time are 
again discharged. Bothingi-ess 
and egress are observed to 
take place only at the posterior 
end.* De Bary stated that 
swarm- cells derive their sup- 
port only from nutrient matter 
in solution, t and it may be 
that they are to some extent 
a to/. Successive stages in bipartition of nourished in this manner; 
swarni-cell, accompanied by the division of the but Considering the large num- 
nucleiis by kai-yokinesis. Magnified 1200 times, n i- • i i ,• „ 4.^ 
Drawn from stained preparations in Canada Oer ot SpecieS belonging to 
tiaisam. different genera which have 
been observed to prey actively 
on bacteria, it cannot be doubted that these form an important 
part of then- food. 
Bipartition of the swarm-cells is observed to begin in a few 
hours after they leave the spore-membrane, and we may conclude 
with de Bary that the process is frequently repeated, for it may 
be seen consta,ntly taking place for three or four consecutive days 
in cultivations, during which time the numbers increase very 
largely. The bipartition is preceded by the withdrawal of the 
flagellum and the swarm-cell taking a spherical form. The 
nucleus then divides by karyokinesis. The earliest stage which 
I have observed is that of the nuclear-spindle with an equatorial 
* Lister, " On the Ingestion of ]fond Material by the Swarm-Cells of 
Mycetozoa.'" Linn, Soe. Jovrn. Hot., 1889, vol. xxv., p. 435. 
t De Baiy, " Comp. Morph. and Biol. Fimgi, Mycet.," etc., p. 452. 
FlO. 2.— AMAUEOCHiETE ATBA Bost. 
