THE SIMPLEST FORMS OF LIFE 33 
and needing moisture for its growth. If threatened 
with drying up it may contract and secrete a protec- 
tive covering about itself. 
The reproduction is purely non-sexual, and consists 
in the breaking up of the protoplasm into a great many 
parts, as in the Monera; but in the slime-moulds the 
cells thus formed secrete a definite protective covering 
or cell-wall, and closely resemble the spores or repro- 
ductive cells of the Fungi, with which these organisms 
are often classed ; but the general opinion at present 
is that they are forms allied to the Monera, which have 
not yet become sufficiently differentiated to show defi- 
nite animal or plant characters. 
The most specialized forms among the slime-moulds, 
like the ones figured (Fig. 4), show a curious resem- 
blance to true plants in their reproductive parts, 
although these resemblances are purely superficial. 
Thus they form spore-cases or “ sporangia” of definite 
and characteristic shapes (B), within which the proto- 
plasm divides into a great many nucleated fragments, 
as in the Monera; but here, as we have seen, each por- 
tion secretes a definite cell-membrane and forms a 
spore, much like an ordinary plant-cell (Fig. 4, C), 
and capable of being dried up without losing its vital- 
ity. With these spores are found in the higher forms 
curious thread-like structures of various kinds. 
The spores, on being placed in water, soon burst open 
and set free the contained protoplasm, which assumes 
the form of a free-swimming, naked cell or swarm- 
spore, like that of the Monera, and resembling closely 
certain low animal forms, the flagellate infusorians 
(Fig. 4, D). In this condition the slime-mould con- 
D 
