Regeneration of ciliary pattern in longitudinal fragments of the hypotrichous ciliate, Stylonychia

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Abstract
Longitudinal fragments of the hypotrichous ciliate Stylonychia were studied at various stages of cortical regeneration by Scanning Electron Microscopy. Analysis showed that (except for the oral primordium) all primordial fields responsible for replacing excised ciliature develop in continuity with existing primordia; i.e., all ciliary primordia are derived from segments originally continuous with the oral primordium. This observation leads to the concept of a single primordial field, a “primordium of the ciliature,” possessing the developmental competence of giving rise to a complete set of ciliary structures. Such a concept implies the operation of a reciprocal intra‐cortical communication system; i.e., the developmental manifestations of any individual primordium are determined at least in part by the precise location of morphostatic and/or primordial ciliary structures. An intra‐cortical communication system is consistent with the previously proposed “determinative region” (Grimes, '75), the function of which is to serve as the initiation site of a primordium during excystment morphogenesis.