Paracrystalline Arrays in the Mitochondria of the Peritrichous Ciliate Carchesium polypinum^,

SYNOPSIS Intramitochondrial inclusions of a paracrystalline nature were observed in the peritrichous ciliate Carchesium polypinum This ciliate was found growing in the effluent of a sewage treatment plant. When paracrystalline inclusions were present, there was one per mitochondrion. A variety of profiles was encountered, all presumably of the same structure. Cross‐sections revealed packed, spherical masses of 100‐150 A diameter with dense walls 30‐40 A thick and a variety of core densities. In more longitudinal sections the paracrystalline array appeared as long. electron‐dense, finely filamentous elements oriented in parallel arrays and regularly spaced with a diameter of 60‐100 A. Mitochondria tended to cluster, and between closely apposed mitochondria a dense, amorphous material was present. Numerous bud‐like processes projected from mitochondria. Structural evidence, particularly the arrangement and core densities of these arrays, suggests a filamentous type of viral infection.