The proboscis of Didinium. While not well preserved, this image clearly shows the clockwise surface ridges that are elevated by ribbons of microtubules that are involved in supporting the buccal cavity during the process of ingesting prey. See the ribbons of microtubules in CIL:17451, 17452, & 15400. The extrusive organelles toxicysts and pexicysts reside just below the membrane of the proboscis plateau. This micrograph was taken in 1968 by G. Antipa on a Cambridge Mark IIA operating at 20kV. The negative magnification is 4760X. 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 and 1970. Capture and ingestion of Paramecium by Didinium nasutum. J. Protozool. 17:250-270.