170 The Nature of Biological Diversity 



ture between vestibule and gullet, is a single kinety, the endoral 

 kinety. The left side of the gullet is composed of two groups of four 

 rows of kinetosomes each, the dorsal and ventral peniculi. The dorsal 

 side of the gullet is made up of a group of four rows of kinetosomes, 

 the quadrulus. Between quadrulus and endoral kinety, the right side 

 of the gullet is composed of what is called the ribbed wall ( Ehret and 

 Powers, 1959), believed to consist of an unknown number of highly 



B ^_ 



FIG. 2. The oral apparatus of P. aurelia. A. Vestibule («), mouth (m), and 

 funnel-shaped gullet (g), viewed from right side, in specimen prepared by modified 

 Regaud hematoxylin technique. The positions of the unseen gullet kineties are 

 indicated by the letters used to symbolize them in B and C. B and C. Two focal 

 levels of silver preparation of oral apparatus viewed from its right side; photo- 

 graphed with bright-field objective and phase contrast condenser. Magnification: 

 2,100 X. B. High focal level showing endoral kinety (e) on right side at juncture 

 with vestibule. C. Low focal level showing quadrulus (q) of dorsal surface of 

 gullet and the two peniculi (p) of the left side of gullet. The two peniculi are so 

 close together as to look like one structure. 



modified kineties. The ribbed wall is located to the observer's left of 

 the endoral kinety in Fig. 2B, but it does not regularly show with the 

 technique employed and is missing from this photograph. 



The orientation of the kineties, for example, those in the left an- 

 terior field, sometimes seems ambiguous in the photographs, yet 

 microscopic examination leaves no doubt. This requires some ex- 

 planation, which can best be given by some further information on 

 the composition of the cortex and its relation to the dots in the photo- 

 graphs. The cortex is a gelated surface layer 1 to 2 microns thick. (As 



