Page:Natural History, Mollusca.djvu/167

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155
LIMPETS.

These habits were first made known by Mr. Lukis, a naturalist of Guernsey, to whom we are indebted for other interesting notes on the economy of animals. "The locomotion of the Limpet," he observes, "may be ascertained by marking one individual to avoid mistake, and then observe its cautious roaming and regular return to its favourite place of rest, where the shell will be found exactly to correspond with the surface of the rock to which it is attached. Here it will rest or sleep, and only relax its strong adhesion to the rock, when the muscular fibre becomes exhausted by long contraction, in which state a sudden blow, horizontally given, will easily displace it. A fact known to the fishermen and poor, who use them for food, is, that they are more easily collected in the night time than in the day. May not this be the period of roaming for food as well as when covered by the tide?

"The march of the limpet is slow and formal; and whenever the cupping process is renewed, the posterior end of the shell is brought in contact with the rock, which is of a soft nature, and will receive the impressions of its denticulations. The track of an individual placed under surveillance was thus made visible over a space of several yards, possessing the same regularity and disposition, and was further remarkable for the constant revolution on its left.

"The tracks of the limpet on granite and other hard rocks, present, at first sight, the same appearances; but, on a closer examination, they are found to differ. When first observed in 1829, a large portion of a fine-grained sienitic rock was traced over by these shells; the remainder was