﻿p. TnoMSOiir, — A Hock Pool and its Contents. 221 



of the leaves of these plants there were crowds of little globules of air — this 

 being oxygen gas, which the plants elaborate from the carbonic acid given off 

 by the animals which lived in the pool. 



Carefully removing some of the vegetation, so as to allow of more light 

 getting into the water, we disturbed a small brown fish, evidently a member 

 of the Goby family, from its bluff-shaped head, and from a habit of attaching 

 itself to the pei'pendicular sides of the pool, the ventral fins being shaped some- 

 thing like a sucker. The little fellow eluded capture very cleverly, and glided 

 hither and thither until it was finally lost in a dark nook at one end. Below 

 the weed at one point there was a colony of those pretty animals the Serpulce, 

 •which live in calcareous tubes, twisted lilce a snake. They are annelids, and 

 have a number of beautiful feather-like tentacles round their head, protruding 

 from their shell, by which they grasp their prey. One of these tentacles is 

 swelled out, and placed on a slightly longer stalk than the others, and forms a 

 sort of cork, by which the animal shuts itself into the shell when alarmed. 

 The Serjndce are said to have no eyes, but they must have something which 

 serves them quite as well, for if the band is drawn quickly across the surface 

 of the water so that the shadow falls upon them, they instantly disappear. 

 After waiting a little the cork will be seen to protrude, slowly followed by the 

 rest of the organs. There were plenty of the common Barnacle in the pool, 

 the rock being studded ^vith them here and there. They ai*e cirrhipeds, throwing 

 out a number of bent arms covered with fine hairs, placed something like the 

 fingers on one's hand ; these they are constantly opening and shutting, of 

 course conveying to the stomach v,diatever articles of sustenance they may 

 happen to inclose. Adhering to the rock were some small molluscs, much 

 resembling a Nerita, and one Limpet [Patella), These are gasteropods, and 

 creep over the rocks on a broad foot ; their mouths are furnished with a very 

 peculiar tongue, rough like a file, and with it they sci-ape the surfaces of the 

 rocks and plants as they travel hither and thither, so keeping down the growth 

 of plants, which would otherwise fill the pool to the exclusion of all else. 



Carefully lifting and turning over a stone which lay at the bottom, quite 

 a crowd of crustaceans was discovered. However, they mostly scuttled away 

 so rapidly that they were lost sight of; but one sort remained : this was the 

 Porcelain crab, of which there were several specimens. These crabs are very 

 peculiarly constimcted, and are so named from the under sides of the bodies 

 resembling porcelain. They mostly inhabit dark places, under stones, etc., 

 and are armed with large powerful nij^pers, though they are quite harmless, 

 and may be handled with impunity. These little creatures are wonderfully 

 adapted to the circumstances in which they live. Theii* bodies are quite thin 

 and compressed, so as to be able to wriggle themselves into any hole or under 

 a stone, where they lie quite out of the reach of any harm. A very minute 



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