Fine Structure of the Schizont Stage of the Testate Marine Ameba, Trichosphaerium sp.*

SYNOPSIS. The schizont stage of 3 strains of the testate marine ameba, Trichosphaerium sp., was examined in the transmission electron microscope. The cytoplasm of this multinucleate organism contained the usual organelles; the test was covered by spicules. Pseudopodial types included broad ectoplasmic lobopods that assisted in locomotion, and thin dactylopods that probably had a sensory function. Nuclear division, observed in one of the strains, was characterized by an intact nuclear envelope (at least through anaphase), and the absence of centrioles. Nuclei in an ameba divided synchronously. An unusual intranuclear body of unknown function was found in another of the strains examined.