1. A cone-shaped structure. 2. Part of the apical complex characteristic of the protozoan subphylum, Apicomplexa; seen in sporozoites, merozoites, or other developmental stages of sporozoans, less well developed in the piroplasms (families Babesiidae and Theileriidae). The function of the c. is unknown, but it is thought to be an organelle of penetration into the host cell, possibly aided by a protrusible form of the c. [G. konoeides, cone-shaped]
Sturm's c. in optics, the pattern of rays formed after passage through a spherocylindrical combination.
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