432 THE AMERICAN NATURALIST [Vol. LIV 



all the lessening degrees, to actual cessation. Usually 

 the beating, no matter what the rate, is regular, i.e., the 

 durations of opening and closing being of equal length. 

 This, however, is subject to modification, apparently at 

 will, and individuals are sometimes, though not fre- 

 quently, encountered in which the lips beat with great 



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