858 



MR. E. S. RUSSELL — EXVIROXMEXTAL 



[Nov. 26, 



During a whole month, therefore, the relative positions of these 

 limpets remained practically unchanged. One of them. No. 3, 

 was almost surrounded by barnacles, to which its shell fitted 

 accurately. 



The relative positions of another series of limpets for various 

 dates during a month are given in Table II. The sizes ranged 

 from 8'5 mm. to 34 mm. The stone on which they were lay near 

 low-water mark, and was largely overgrown with Ficcus. 



Table II. 



At first sight these data seem contradictory of those in Table I., 

 but the inconsistencies can be easily explained. The limpets in 

 Table I. are all large ; in Table II. only Nos. 1, 3, and 4 are more 

 than 30 mm. long. The relative positions of Nos. 1, 3, and 4 ai-e 

 very constant. No. 2 in Table II. is a limpet 8-5 mm. in length, 

 and the great variation of its distance from No. 1 (30-5 mm. long) 

 covers the fact that No. 2 wandered, while No. 1 was quite 

 stationary. Nos. 7 and 8 are small limpets — both under 15 mm. 



and both wandered a good deal. Nos. 5 and 6 are limpets 



20 mm. and 24 mm. long respectively, and their relative distance 

 (and also No. 5's distance from No. 4) shows on the whole quite 

 small variations. The greatest variation of No. 5's distance from 

 No. 4 is that given under date 7th July, when the distance was 

 65 mm. as against the usual 49 mm. On this occasion it was 

 No. 5 which had moved, while No. 4 had not changed its 

 position. 



The conclusion may be drawn therefore that large limpets are 

 more fixed in their position than small limpets. It will be noticed 

 that double measurements are given for the distances of Nos. 4 

 and 5, and 5 and 6, under the date 10th July, and further, that the 

 second measurement in each case is the same as that made on the 

 30th June. The explanation is rather interesting. On 10th July 

 the first measurements (those in brackets) had just been made 



