Cilia 651 



port of the axial filament as the active portion one can point to the terminal 

 undulation of the flagellum of Peranema. This portion of the organ ap- 

 pears to possess principally the axial fiber. 



The ciliary activity normally involves a utilization of oxygen, the rate of 

 02-consumption varying with ciliary rate.-'^ However, like muscle, cilia ap- 

 pear capable of acting for a time anaerobically. After administration of 0.1 

 per cent NaCN to a fragment of Mytilus gill, O2 consumption drops off 

 abruptly, yet ciliary activity diminishes much more slowly. Fragments of 

 Mytihis gill placed in weak hemoglobin solutions in chambers perfused 

 with damp hydrogen show ciliary beat continuing for some time after reduc- 

 tion of the hemoglobin. After ciliary beat has become very slow under the 

 anaerobic conditions, rapid beat is restored quickly on readmission of oxygen 

 and reoxygenation of the hemoglobin. The cilia of the gill of Pecten, on the 

 other hand, are reported to cease beating immediately on removal of oxygen,^" 

 as indicated by the reduction of dyestuffs such as janus green and neutral 

 red, and before nile blue is reduced. The cilia of Paramecium cease activity 

 within a few seconds in an O^-free medium.^"^ It is known, nevertheless, that 

 some ciliates are able to carry on normal ciliary movement in natural envir- 

 onments which are practically oxygen-free. One can not yet conclude whether 

 the need for O2 differs qualitatively or only quantitatively among different 

 species of animals. 



REFERENCES 



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3. Brown, Harley P., Ohio ). Sci. 45:247-301 (1945). Structure of protozoan 

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8. Chase, A. M., and Glaser, O., /. Gen. Physiol. 13:627-636 (1930). H-ion con- 

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15. Foster, E., Baylor, M. B., Meinkoth, N. A., and Clark, G. L., Biol. Btill. 93: 

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16. Gemmill, J. F., Proc. Zool. Soc. London 1-19 (1915). Ciliary activities in echino- 

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