The conoid (Kinete/Fig. 2, Pellicle/Fig. 5B) is a hollow truncated cone composed of spiralling microtubules 25 nm in diameter. Two accessory structures, the conoidal or preconoidal rings, form an integral part of the conoid and they are connected with each other by a canopy-like membrane. During cell penetration the conoid protrudes through the anterior polar ring system. The conoid is apparently involved in penetration of host cells. Conoids are found in the motile stages of some coccidia, such as Eimeria, Sarcocystis and Toxoplasma (Kinete/Fig. 2, Pellicle/Fig. 5), but are always absent from the corresponding stages of haemosporidians (e.g. Plasmodium) and piroplasms (Babesia, Theileria).