INTRODUCTION.
5
plate and an indication of spindle-fibres converging at the poles ;
at a later stage the swarm-cell becomes ellipsoid and a constriction
appears in the middle. A s bipartition proceeds the nuclear plate
divides and the two halves separate, the connecting achromatic
fibres being often discernible. The daughter-nuclei at length
retreat to the opposite poles of the swarm-cell, which in about a
quarter of an hour from the beginning of the process of con­
striction is completely divided. A flagellum is in a short time
produced by each, daughter-cell, which then assumes the original
form of the parent. After dividing in the manner described,
through a period of uncertain duration, they withdraw the
flagellum and creep with slow amoeboid movement. When two
of them come in contact with each other they may coalesce;
others congregate at this point and form a centre to which great
numbers converge, and though they may remain distinct for
some time, ultimately unite and mingle into one moving mass,
the plasmodium of Cienkowski.
There is no doubt that the
young plasmodia exercise a
distinct attracting influence
on the swarm-cells in their
neighbourhood. Many amoe­
boid swarm-cells, after re­
maining some time near the
Plasmodium, contract and form
into microcysts, in which state
they are enclosed by the plas­
modium and become sur­
rounded with vacuoles, where
they are gradually digested.
Although the fusing swarmFIG. 3.—DIDYMIUM DIFFORME Duby.
cells thus lose their mdividu.
.
- .
„
loung plasmodium, with attendant amoeboid
allty, their nuclei, SO rar as swarm-cells, some of which have turned into
has been observpd remain
°y
6») : one microcyst is being digested
nas_ Deen ODberveu, remain
a vacuole (v). An empty spore-shell is shown
distinct. For example, eight at*.
m i c r o
s t e
i n
T,
i
? T
Magnified 470 times.
swarm-cells may be counted
uniting and forming a Plas­
modium, and their eight nuclei can be afterwards distinguished;
but when this number is exceeded the movements of the Plas­
modium and the inconspicuous nature of the nuclei present
difficulties in the way of their recognition. Whatever reason
there may be from general considerations to regard this fusion
of individuals as akin to conjugation, no fusion of nuclei, which
appears to be an essential part of the process, has yet been
observed.
In the Exosporew represented by the single genus Ceratiomyxa,
the spore is ellipsoid, and consists of granular protoplasm, in
which four nucleus-like bodies can often be observed. This is
enclosed by a membranous and colourless spore-wall. On placing
the perfectly matured spores in pure water, the membranous