Contradictory statements have been made as regards several important
points in the development of the statoblast and it is probable that
considerable differences exist in different species. The following facts
appear to be of general application. The cellular contents of the
capsule consist mainly of a mass of cells packed with food-material in a
granular form, the whole enclosed in a delicate membrane formed of flat
cells. When conditions become favourable for development a cavity
appears near one end of the mass and the cells that form its walls
assume a columnar form in vertical section. The cavity increases rapidly
in size, and, as it does so, a young polypide is budded off from its
walls. Another bud may then appear in a similar fashion, and the
zooecium of the first bud assumes its characteristic features. The
capsule then splits longitudinally into two disk-like valves and the
young polypide, in some cases already possessing a daughter bud, emerges
in its zooecium, adheres by its base to some external object and
produces a new polyparium by budding. The two valves of the statoblast
often remain attached to the zoarium that has emerged from between them
until it attains considerable dimensions (see Plate IV, fig. 3 _a_).
What conditions favour development is a question that cannot yet be
answered in a satisfactory manner. Statoblasts can lie dormant for
months and even for years without losing their power of germinating, and
it is known that in Europe they germinate more readily after being
subjected to a low temperature. In tropical India this is, of course, an
impossible condition, but perhaps an abnormally high temperature has the
same effect. At any rate it is an established fact that whereas the
gemmules of most species germinate in Europe in spring, in Bengal they
germinate either at the beginning of the "rains" or at that of our mild
Indian winter.
MOVEMENTS.
[Illustration: Fig. 32.--Zoarium of _Lophopodella carteri_ moving along
the stem of a water plant, × 4. (From Igatpuri Lake.)]
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