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. As 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 amceboid 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 swarm- 
cells thus lose their individu- „ 
.1 • ^ 1 • p loung pJasmodaum, with attendant amoeboid 
allty, tneir nuclei, so lar as swarm-cells, some of which ha-ve turned into 
has been observed, remain T ^ 
, . J . , _^ ' . , ma vacuole (v). An empty spore-shell is shown 
distinct. Jbor example, eight ats. 
swarm-cells may be counted Magnified 470 times, 
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 
difiiculties 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 Exosporece 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 placino- 
the perfectly matured spores in pure water, the membranous 
Fig. 3.— Didyjiium diffoeme Duby. 
