STONE-TURNING. 37 



tiny creatures would be seen agilely swimming from 

 weed to weed, or lithely twining among the fronds, 

 which now we have to search for in their recluse hiding- 

 places under these rocks. 



Selecting a stone which experience teaches us is a 

 likely one and only experience can teach this, though in 

 general I may say that the heaviest and flattest beneath, 

 those which appear to have been long undisturbed, and 

 especially those which, instead of being imbedded in 

 the soil, rest on other stones in such a partial way that 

 there is room for free ingress and egress to minute 

 creatures beneath, and which have a broad surface to 

 which they may cling in congenial darkness, are the 

 most promising selecting, I say, such a stone, we place 

 both hands beneath one side, and heave with all our 

 might to turn it bodily over. We must be careful, for 

 many of these stones are so beset with the small shells 

 of Serpula triquetra, that they cannot be handled with 

 impunity. This is a worm which makes a tubular pipe 

 for its defence, of hard shell, adhering to the rock 

 throughout its length ; the tube enlarges a little as it 

 grows, and its most recent extremity, which is bril- 

 liantly white and clean, is defended by the projecting 

 extremity of a ridge which runs along the back of the 

 shell, the point of this ridge forming a very sharp 

 needle-like prickle, which, as we apply our hands be- 



