Sometimes low water will occur after dark. Do not be deterred by the darkness, but take a lantern and go on with your researches. You will be rewarded for your trouble, as there are in the sea, as on the shore, many creatures which hide themselves during the day and only move about at night.
Such, for example, are the limpets. In the daytime they are motionless, and fixed so firmly against the rock that they are not easily removed. Each limpet has the edges of its shell sunk into a slight hollow, which the shell exactly fits. If a shell be marked, say with a little red sealing-wax varnish, and its locality marked in the same manner, it seems to be absolutely stationary, never leaving the spot where it was first marked.
But if the observer takes a lantern to the same locality at night he will find the marked spot vacant, its tenant having gone off to feed on the algae. Hundreds of limpets may be seen slowly travelling about during the hours of darkness. Towards dawn, however, they cease from feeding, and go back to their resting places, each having its own simple home, and not allowing any of its companions to intrude upon its territory.
As a rule, very few living creatures will be found until midway between high and low water mark, and those which are found are generally damaged or half-dead. But when you have reached the midway line you may begin your search in good earnest. Do not take too large an area, nor be in haste to pass from one spot to another, as is the custom of all beginners. Choose a single small rock-pool, and make up your mind not to leave it until every inch of it has been minutely examined. Nothing sharpens the eyesight more than your practice, and after a while you will find yourself detecting objects which would have eluded your observation a few days ago.
Turn over every stone, peep into every crevice, and try them not only by the eye but with the fingers. Touch often succeeds where sight fails, and many Actinia or Nudibranch would escape if the shore-hunter were to use his eyes without supplementing them with his fingers.
(To be continued)