1907.] STUDIES ox THE LIMPET. 859 



when I noticed that No. 5 was moving. Nos. 4 and 6 made no 

 movement. No. 5 crept a few millimetres, and fitted the indenta- 

 tions of the hinder edge of its shell to three barnacles adhei-ing 

 to the stone. It then settled down as if for good, and moved no 

 more. On re-measuring its distances from No. 4 and No. 6, I 

 found them to be identical with the distances measured on 30th 

 June. Evidently the positions of No. 4 and 6 were definitely 

 fixed, and No. 5, too, had a definitely fixed place of abode and was 

 able to find its way back thereto with astonishing accuracy. 



On the 26th and 30th July I noticed that the weed growing on 

 the stone had covered over most of the limpets and so kept them 

 moist. I believe that under these circumstances the limpets, 

 especially the small ones, moved about a little more than usual, 

 and did not return so carefully to their fixed positions. The 

 figures certainly show considerable variations for these dates. 



I kept records also of the movements of five small limpets, « (10 

 mm.), h (13 mm.), c (4 mm.), d (7 mm.), and e (5"5 mm.). They 

 were under observation at intervals for over three weeks. The 

 records may be summarised as follows -.—a was to be found always 

 within a few centimetres of one fixed spot, and on the 11th, 12th, 

 and 30th July was found on that spot, with its shell fitted to a 

 Sjyirorhis-tvCbe and to a barnacle. On the 30th July I saw it 

 move to the spot and adjiist itself. Limpet h was more irregular, 

 and did not seem to have a fixed stance, but it was always to be 

 found near at hand. Limpet c changed its position by a few 

 centimetres from time to time. Limpets d and e occupied on 5th 

 July a definite position on a clearly marked circular space on a 

 stone. On the 10th, 11th, 26th, and 30th of the same month 

 they occupied exactly the same positions. On the 7th they were 

 distant 4 cm. and 8 cm., evidently in search of food. On the 12th, 

 at 9.30 A.M., e was in position, d 3 cm. away. The stone had just 

 been uncovered, and d was on its way " home." Twenty minutes 

 latei' I found d in jjosition. These two limpets therefore had^a 

 definite home, to which they returned when the tide left them 

 high and dry. 



A well-known fact which goes far to pi-ove the homing habit 

 of Patella may here be mentioned. One may often find on the 

 shore a limpet quite surrounded and hemmed in with barnacles. 

 If one knocks the limpet off one finds a clear space on the rock 

 below, the outline of which, formed by the barnacles, closely follows 

 that of the limpet's shell. Another fact of the same kind may often 

 be observed. If a large limpet adhering to a smooth surface of 

 rock be detached, a dark " weathering," of shape corresponding 

 to the limpet's, will usually be seen. 



The former of these facts afiords a simple method of deter- 

 mining the size at which a limpet settles down to a fixed abode. 

 I have not seen any below 10 mm. in length occupying a definite 

 position marked out by barnacles. Near low-water mark the 

 average size at which limpets settle down seems to be, as 

 determined by this method, about 15 mm., though I have seen 

 Proc. Zool. Soc— 1907, No. LYIIL 58 



