The aboral view of Didinium showing seven contractile vacuole pores for it's single posterior contractile vacuole and metachronous waves of cilia in one of the two characteristic ciliary girdles of Didinium nasutum. To one side you will note five white lines that represent rows of clavate cilia (also seen in CIL:17891 and CIL:19538). The bumps you will see on the surface at higher magnification may be either solitary clavate cilia or cyrtocysts, an extrusive organelle of unknown (possibly defensive) function. A thin section of a cyrtocyst can be seen at CIL:4665. This micrograph was taken in 1968 by G. Antipa on a Cambridge Mark IIA operating at 20kV. The negative magnification is 825X. The raw film was scanned with an Epson Perfection V750 Pro. This image is available for qualitative analysis. Further details are available at Wessenberg, H. and Antipa, G. 1968. Studies on Didinium nasutum. I. Structure and ultrastructure. Protistologica 4:427-447.