Studies on the embryogenesis of the tapewormCittotaenia variabilis (Stiles, 1895) using transmission and scanning electron microscopy

The embryogenesis of the tapewormCittotaenia variabilis from the oocyte to the oncosphere is followed using scanning electron microscopy (SEM) in conjunction with ethanol cryofracture. Transmission electron micrographs and histochemistry are used to corroborate the inferences drawn from the SEM studies. Evidence is given for oocyte granules, the uterine epithelium, and the outer envelope as sources of components for the outer capsule. The contributions and senescence of the inner envelope and its relationship to the embryophore are given.