58 



MORPHOGENESIS IN CILIATES 



the same time the other ciliary rows are rolled up at the 

 posterior end into a sinistral spiral coil. This spiral coil 

 then suddenly disappears. It has been invaginated into the 

 posterior end. This apart, the tomite shows nothing re- 

 markable. The anterior part of the row x will give rise to 



Fig. 24. Foettingeria actiniarum. Growth of the trophont. The de- 

 torsion accompanying the increase of size is clearly visible. The smallest 

 trophont (a) is 29 fi long. The largest (c) is 60 /i. Compare with 

 the 160-Ai-long trophont of Fig. 21. 



the rosette or mouth organ which has the same structure 

 and size in the tomite as in the adult. The spiral coil 

 formed and invaginated during the tomitogenesis of Foet- 

 tingeria will be extruded during the phoretic phase. But 

 the extruded spiral will be dextral, that is to say, have an 

 inverted direction. Thus it is obvious that torsions of the 

 cytoplasm may take place independently of elongation of 

 kinetodesmas. 



This is certainly a very rare, if not unique, example of 

 the succession of a dextral and sinistral structure in one 



