CHAPTER 10 



Movements of the Ciliary System 

 in Ontogeny and Piiylogeny 



An interesting and homogeneous group of ciliates lives in 

 the mantle cavity of bivalve molluscs. Among them is the 

 family of Hemispeiridae (= Ancistrumidae) . The somatic 

 system of kinetics is formed by longitudinal anteroposterior 

 rows with short cilia. A small sector of this somatic system 

 is thigmotactic. The preoral and oral systems are formed 

 by two long curved rows, having very long cilia, and ending 

 in the posterior oral infundibulum. 



The three genera Ayicistrurn, Proboveria, and Boveria are 

 characterized and defined by the position of the origin of 

 the preoral system: anterior in Ancistrum, median in Pro- 

 boveria, posterior in Boveria. These three genera represent 

 three steps of an orthogenetic evolution: Ancistrum being 

 the primitive type, Proboveria intermediate, and Boveria 

 extreme [E. Chatton and A. Lwoff (1949)]. 



We shall first examine the division of Proboveria. Before 

 any visible sign of cytoplasmic constriction, the somatic 

 kinetics are cut approximately in their middle. The oral 

 system has migrated towards the anterior pole. The kine- 

 tics have become elongated and the kinetosomes have mul- 

 tiplied. The kinety 1, which is stomatogenic, will give rise 

 to various kinetics: kinety B and pharyngeal kinetics. 

 When the morphogenesis of the preoral and oral systems is 

 completed and when the proter and the opisthe are ready to 

 separate, they show the typical structure of the genus An- 

 cistrum. During growth, the preoral and oral systems w^ill 



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