172 The Nature of Biological Diversity 



meridians, and the two sets of 5 kinety fields adjacent to them. 

 Between the two sets of structures, there is no partition. They appear 

 to converge at a single anterior pole and a single posterior pole near 

 the ends of the longitudinal axis. As one looks to the animal's right 

 from the upper oral meridian in Fig. 3 A, one sees first the usual three 

 right kinety fields (anterior, circumoral, posterior) on the extreme 



cvp 



a r 



m 



FIG. 3. Doublet animal at two focal levels: A, surface at upper focal level; B, 

 surface at lower focal level. Silver preparation. Note that on A (upper surface) the 

 animal's right is the observer's left; but on B (lower surface) the animal's right 

 is the observer's right, a, anterior pole; al, anterior left kinety field; ar, anterior 

 right kinety field; cvp, contractile vacuole pore. (The third dot on each contractile 

 vacuole pore meridian is an artifact.) g, gullet; m, mouth; ma, macronucleus; p, 

 posterior pole; pr, posterior right kinety field; pi, posterior left kinety field; py, 

 cytopyge; v, vestibule with right circumoral kinety field. 



left side of the photograph. Continuing to the animal's right, by focus- 

 ing down on the left from Fig. 3A to 3B, interpolar dorsal kineties 

 come into view and in their midst is the contractile vacuole pore 

 meridian (or few meridians) . This wide dorsal kinety field grades into 

 the three left kinety fields (anterior, circumoral, posterior) which 

 border on the second oral meridian seen near the right edge of Fig. 

 3B. The whole sequence of areas is again repeated in passing further 

 to the right arovmd to the starting oral meridian: the second set of 

 right kinety fields is on the extreme right of Fig. 3B; continuing to 



