52
On the occurrence of the Rhizopod,
was first found by Cienkowsky near St. Petersburg on water-
plants (Nitella and Vaucheria), and was described by him, in
1867, in Schultze's 'Archiv fur Mikroskopische Anatomie.'
It was also found by Haeckel near Jena, and by Greet near
Bonn; and the form was subsequently detected by Mr. W.
Archer in the Callery-bog near Bray, and in Co. Tipperary,
Ireland; also in Wales; and by Dr. Leidy in N. America.
Mr. Archer at first described it (not being aware of Cien-
kowsky's discovery) under the name of Podosphaeria haeckel-
liana (Quart. Journ. Micros. Soc. viii. (1868) 67). It was
always found very sparingly; but Mr. Archer was disposed
to think that its distribution would be found to be pretty
wide, although perhaps rare in individuals, and restricted to
isolated spots. The structure of Clathrulina seems to show
that it is a protozoon allied to the fresh-water Heliozoa (of
which Actinophrys sol may be taken as an example), and
connecting that well-known form with the marine Radiolaria
(the Polycistina of Ehrenberg). It is an exquisitely beautiful
object, the protoplasmic body-mass being contained in a
superb latticed globe of silica, reminding one of the carved
ivory balls cut by the skilfully-patient hands of the Chinese
artisans. Figures of it in its various stages will be found in
Dr. Leidy's magnificent work, 'The Fresh-water Rhizopods
of North America,' forming volume xii. of the United States
Geological Survey of the Territories (1879). The peduncle
by which it is attached to its point of support is very flexible
and of varying length ; and in mature individuals, according
to Leidy, the homogeneous granular protoplasmic body
occupies only the centre of the globular capsule, leaving a
space between it and the circumferential walls. Thread-like
prolongations of the protoplasm are extruded through the
foramina of the capsules, subserving the prehension of food,
in the manner so frequently witnessed by microscopists in
the case of the common Actinophrys of our ditches and ponds.
Reproduction appears to take place in four ways :—(α) By
fission, as observed by Cienkowsky—the protoplasmic body
dividing into two (rarely four) simple granular spheres which
pass out of the silicious capsule, and subsequently develop
each a stem, and still later a foraminated capsule of its own.
(b) By the throwing off of small sarcode bodies, as apparently
observed by Mr. Thomas and described above in his notes,
which subsequently pass through an Actinophrys-like stage,
and then secrete the characteristic silicious capsules, (γ)
Hertwig and Lesser describe (Archiv. fur Mik. Anat. 1874) a,
third mode in which the body-mass breaks up into a number
of smaller masses, each of winch becomes surrounded by an