A cilium (plural cilia) is an organelle found in eukaryotic cells. Cilia are tail-like projections extending approximately 5–10 micrometers outwards from the cell body.[citation needed] There are two types of cilia: motile cilia, which constantly beat in a single direction, and non-motile cilia, which typically serve as sensory organelles. Along with flagella, they make up a group of organelles known as undulipodia.
Cilia may be "viewed as sensory cellular antennae that coodinate a large number of cellular signaling pathways, sometimes coupling the signaling to ciliary motility or alternatively to cell division and differentiation".
Cilia History of Discovery
Cilia were appendages which were described by Ehrenberg in the Bacterium trilocular.
Recent researches permit us to say that cilia exist without doubt in all the true bacteria, Bacillus, Bacterium, Spi rillum. They have been perceived in a great number of forms, Spirillum volutans, Sp. Undula, Vibrio rugula, Spiromonas Cohnii, Vibrio ser pens, and several species of Bacillus. It is only in the smallest of the bacteria that it has hitherto been impossible to demonstrate their presence.
Cilia have, however, been recently seen by Dailinger and Drysdale in Bacterium termo. Warming has perceived as many as two or three on one extremity in Ophidomonas sanguinea Spirillum volutans var. Robuslum, arid Vibrio rugula.
