10 TRANSACTIONS, NATURAL HISTORY SOCIETY OF GLASGOW. 



natural haunts, I placed over it an arch made from 

 a piece of iron hoop ^vith a ^vire let down through 

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

 when the animal left its place the ware dropjDed 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 x^i'essure of the waves when the sea. was in 

 any degree rough, a thin brass tube five inches long 

 w^^s fixed in the arch and the wire let doAvn 

 through it, hj wdiich means the lateral motion of 

 the w^ire was reduced to a minimum. The observa- 

 tions w^ere regularly carried on from the 21st June 

 till the 20th August, 1883, and w^ere made on differ- 

 ent limpets and on different zones of the tidal belt. 

 It w as found that no one of the different limpets 

 was regular as to the ]3eriod wdien it w^ent out to 

 feed. The same animal sometimes Avent out for 

 one or tw^o tides consecutively, and at other times 

 alternately, and occasionally not till the third or 

 fourth flow of the tide. Those near high water 

 w^ere less regular than those lower dow^n. This 

 may be explained by those higher uj) 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 w ith young balani w hich 

 surround the limpets very closely. It w^as noticed 

 that there was always a little bare space on one or 

 other side of the shell. In these cases the animal, 

 after being out to feed, was ahvays found back 

 close to the drop wire, as if endeavouring to get 

 back to the exact spot it had left. 



Mr. George Roberts, in the Ann. Mag. Nat. Hist., 

 gives a case illustrative of the precision of the 

 limpet in adjusting itself to the exact spot which it 

 had left, and in this case apparently w^ith a purpose. 

 He says : " Above the level of the water was a 

 smooth place from which a limpet had not long 

 before moved. As the spot was different in colour 



