418 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
Genus TRICHOSPH.ERIUM 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. 
Trichosphserium sieboldi Schneider. Fig. 3. 
With the characters of the genus. A form which 1 have taken to be a young stage of this 
interesting rhizopod is described as follows: 
A minute, almost quiescent, form which changes its contour very slowly. The membrane is cap- 
like and extends over the dome-shaped body, fitting the latter closely. The endoplasm is granular and 
contains foreign food-bodies. Nucleus single, spherical, and centrally located. Pseudopodia short 
and finger-form, emerging from the edge of the mantle-opening and swaying slowly, from side to side or 
quiescent. The most characteristic feature is the presence of a broad, creeping sole, membranous in 
nature and hyaline in appearance. This membrane is the only evidence of ectoplasm, and it frequently 
shows folds and wrinkles, while its contour slowly changes with movements of body. The pseudo- 
podia emerge from the body between this membrane and the shell margin. Contractile vacuole 
absent. Length 42 ju, width 35// . In decomposing seaweeds, etc. 
Only one specimen of this interesting form was seen, and I hesitate somewhat in placing it on 
such a meager basis. It is so peculiar, however, that attention should be called to it in the hope 
of getting further light upon its structure and mode of life. Its membranous disk recalls the genus 
Plakopus; its mononucleate condition, its membranous disk, and the short, sometimes branohed, 
