Electron Microscopy of the Hypotrich Ciliate Oxytricha platystoma, with Consideration of its Macronuclear Organization

SYNOPSIS. The body of Oxytricha platystoma is covered with 2 membranes, the outer or pellicular membrane and the inner or cytoplasmic membrane. Each cirrus consists of a bundle of 25-50 cilia. There are 2 macronuclei and 2 micronuclei. The micronucleus is a very small body containing dense Feulgen-positive material. The macronucleus is an elongated body surrounded by a double membrane. The dense Feulgen-positive material is embedded in a less dense nucleoplasm. Some larger bodies found inside the nucleus may be nucleoli. There is a single reorganization band in each macronucleus. It consists of a solution plane and a reconstruction plane, and has a total thickness of 1.5 μ. The macronucleus divides amitotically, whereas the micronucleus divides mitotically.