large motile
protoplasmic bodies named _plasmodia_. The newly-formed plasmodium is
distinguished by its greater size from the swarm-cells, while it
exhibits essentially the same movements and changes of shape. The
plasmodia gradually increase in size, and as they grow assume commonly
the form of branched strands; these spread over the surface of the
substratum, which is usually the decaying parts of plants, in the form
of veins and net-works of veins, giving rise to a copiously-branched
reticulated or frill-like expansion, which covers surfaces varying in
extent from a few to several centimeters. They are chiefly composed of a
soft protoplasm of the consistence of cream, which may be readily spread
out into a shapeless smear, and is usually colorless, but sometimes
exhibits brilliant colors of yellow, orange, rose, purple, etc. The
development of the plasmodium ceases with the formation of the _spores_
within their _sporangia_.

The formation of the sporangia out of the plasmodium appears under three
general forms, which, however, pass into each other and are, therefore,
not strictly limited.

_First:_ An entire plasmodium spread out on its substratum becomes
transformed into a sporangium, or it divides into a variable number of
unequal and irregular pieces, each of which undergoes transformation.
Such a sporangium lying flat on the substratum, more or less elongated
and flexuous, often branched and reticulate, is termed a
_plasmodiocarp_.

_Second:_ Erect sporangia on a narrow or stalk-like base, begin as
node-like swellings on the branches of the plasmodium, and gradually
rise to their ultimate form as the surrounding protoplasm flows into
them and assumes an upward direction. These sporangia are nearly always
perfectly regular in shape; they may be globose, obovoid, somewhat
depressed, or more or less elongated, and are either stipitate or
sessile.

_Third:_ A number of plasmodia collect together from every side and
become fused into a single body, often of considerable dimensions; from
these combinations originate the large spore-receptacles which are
called _aethalia_. The component sporangia may be regular in shape,
standing close together, in a single stratum, with entire connate walls;
more often, being elongated and flexuous, they branch and anastomose
freely, their walls becoming perforated and more or less defective; in
other cases, the aethalium is a compound plasmodiocarp, the narrow
sinuous sporangi