The Cambridge natural history, Vol. 01 (of 10)Hickson, Sydney J. (Sydney John)
Science
The Cambridge natural history, Vol. 01 (of 10)
Hickson, Sydney J. (Sydney John)
Animals
II. FILOPLASMODIEAE.—_Chlamydomyxa_[97] is a not uncommon inhabitant of the
cells of bog-mosses and bog-pools, and its nutrition may be holophytic, as
it contains chromoplasts; but it {91}can also feed amoeba-fashion.
_Labyrinthula_ is marine, and in its fructification each of the component
cells forms four spores. _Leydenia_ has been found in the fluid of ascitic
dropsy, associated with malignant tumour.
III. MYXOMYCETES.—The fructification in this group is not formed by the
mere aggregation of the zoospores, but these fuse by their cytoplasm to
form a multinucleate body, the "plasmodium," which, after moving and
growing (with nuclear division) for some time like a great multinucleate
Reticularian, passes into rest, and develops a fructification by the
formation of a complex outer wall; within this the contents, after
multiplication of the nuclei, resolve themselves into uninucleate spores,
each with its own cyst-wall. The fructifications of this group are often
conspicuous, and resemble those of the Gasteromycetous fungi (_e.g._, the
Puffballs), whence they were at first called _Myxogastres_. De Bary first
discovered their true nature in 1859, and ever since they have been claimed
by botanist and zoologist alike.
The spore on germination liberates its contents as a minute flagellate,
with a single anterior lash and a contractile vacuole (Fig. 30, C). It soon
loses the lash, becomes amoeboid, and feeds on bacteria, etc. (Fig. 30, D,
E). In this state it can pass into hypnocysts, from which, as from the
spores, it emerges as a flagellula. After a time the amoeboids, which may
multiply by fission, fuse on meeting, so as to form the plasmodium (Fig.
30, F). This contains numerous nuclei, which multiply as it grows, and
numerous contractile vacuoles. When it attains full size it becomes
negatively hydrotactic, crawls to a dry place, and resolves itself into the
fructification. The external wall, and sometimes a basal support to the
fruit, are differentiated from the outer layer of protoplasm; while the
nuclei within, after undergoing a final bipartition, concentrate each
around an independent portion of plasma, which again is surrounded as a
spore by a cyst-wall. Often the maturing plasmodium within the wall of the
fruit is traversed by a network of anastomosing tubes filled with liquid,
the walls of which become differentiated into membrane like the fruit-wall,
and are continuous therewith. As the fruit ripens the liquid dries, and the
tubes now form a network of hollow threads, the "capillitium," often with
external spiral ridges (Fig. 30, A, B). These are very hygroscopic, and by
their expansion and contraction {92}determine the rupture of the fruit-wall
and the scattering of the spores.
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