ABSTRACT
The patterning and organization of new structure in eukaryotic cells can, in certain cases, be controlled by existing structure. Sonneborn illustrated this in Paramecium two ways. (1) Cells with a doublet phenotype (individual cells with almost two complete sets of cortical structures) develop true to type and are inherited, sexually and asexually, independent of changes in nuclear genotype or fluid cytoplasm (Sonneborn, 1963). (2) Inverted rows of cilia and basal bodies maintain their inverted polarity during morphogenesis and cell division, again independent of changes in nuclear genotype or fluid cytoplasm (Beisson & Sonneborn, 1965). These observations led to formulation of the concept of ‘cytotaxis’ – the organization of new structure under the influence of preexisting structure (i.e. the molecular architecture of the cell which includes visible structure) (Sonneborn, 1964,1975). Cytotaxis thus represents an informational system for pattern development and regulation which is not under direct nuclear control. Several examples of cytotaxis have been demonstrated subsequently in other cell types (Grimes, 1973c, 1976; Grimes & Adler, 1978; Grimes & L’Hernault, 1979; Hammersmith, 1976b); Ng & Frankel, 1977).
