326 The Naturalist of Cumbrae. 



put the matter to the test by an ingenious experiment, 

 which he has thus described : 



"To ascertain the movements of the animal in its 

 natural haunts, I placed over it an arch made from a 

 piece of iron hoop with a wire let down through the 

 arch resting on the crown of the shell, so that when 

 the animal left its place the wire dropped on the rock. 

 By this means on visiting the place at each tide, when 

 the shell was uncovered, I could see whether it had 

 shifted or not. To prevent as far as possible the 

 indicating wire being acted on by the pressure of the 

 waves when the sea was in any degree rough, a thin 

 brass tube five inches long was fixed in the arch and 

 the wire let down through it, by which means the 

 lateral motion of the wire was reduced to a minimum. 

 The observations were regularly carried on from June 

 21 till August 20, 1883, and were made on different 

 limpets and on different zones of the tidal belt. It 

 was found that no one of the limpets was regular as to 

 the period when it went out to feed. The same animal 

 sometimes went out for one or two tides consecutively, 

 and at other times alternately, and occasionally not 

 till the third or fourth flow of the tide. Those near 

 high water were less regular than those lower down. 

 This may be explained by those higher up on the 

 tidal belt being for a shorter time and less regularly 

 covered by the tide. The rocks near high water are 

 often thickly covered with young balani * which sur- 



* These may be more familiar to some under the name of cirripedes, 

 a group which so long engrossed the attention of Charles Darwin, and 

 in reference to which he says, " I worked steadily on this subject for the 

 next eight years, and ultimately published two thick volumes, describing 



