[Illustration: Fig. 2.--_Amoeba_ sp.]


Genus TRICHOSPHÆRIUM Schneider '78

Synonym: _Pachymyxa hystrix_ Gruber.

Marine rhizopods, globular or irregular in form, and slow to change
shape. Dimorphic. Both forms multinucleate during vegetative life.
Pseudopodia are long, thin, and thread-form, with rounded ends.
Their function is neither food-getting nor locomotion, but probably
tasting. The plasm of both forms is inclosed in a soft gelatinous
membrane. In one form the jelly is impregnated with needles of
magnesium carbonate (Schaudinn), but these are absent in the other
form. The membrane is perforated by clearly defined and permanent
holes for the exit of the pseudopodia. Reproduction occurs by
division, by budding or by fragmentation, but the parts are
invariably multinucleate. At the end of vegetative life the
needle-bearing form fragments into numerous mononucleate parts; these
develop into adults similar to the parent, but without the spines.
At the end of its vegetative life this new individual fragments into
biflagellated swarm-spores which may conjugate, reproducing the form
with needles. Size up to 2 mm.


Trichosphærium sieboldi Schneider. Fig. 3.

With the characters of the genus. A form which I have taken to be a
young stage of this interesting rhizopod is described as follows: