ABSTRACT
Different species of Ciliates are characterized by the relative positions of the meridional ciliary bands (somatic kineties) and the oral or peristomial ciliary bands. Division sees the formation of two homothetic ciliary systems, one defining the anterior individual (proter) and the other the posterior individual (opisthe).
Urocentrum turbo is characterized by the secondary arrangement of its somatic kinetosomes on transverse annular lines forming a wide anterior girdle or fascia and a narrow equatorial girdle or cingula.
At the first stage of division the cingula grows by the multiplication of its kinetosomes; the distribution of these along the somatic kineties then completes the morphogenesis of the proter and opisthe.
The cingula of Urocentrum is a morphogenic zone which conforms in its actual structure to the provisional idea of a ‘division zone’ introduced by Calkins.
The oral ciliation constitutes an autonomous system with its own morphogenic zone.