THE STUDY OF SHORE ANIMALS. 33 



double shell. The snail-like forms (Gasteropods) 

 have sometimes a coiled shell, sometimes a conical 

 one (limpet), and are sometimes without a shell. 

 They can be generally recognised by the creeping 

 foot and the horns on the head. The cuttles 

 have many arms bearing suckers. All Molluscs 

 have soft unsegmented bodies without appendages. 



Vertebrata are represented on the rocks by Tunicates or 

 sea-squirts with their tough tunics, and by the Fishes, which 

 can be recognised without difficulty. 



This account should enable even the beginner to fix 

 roughly the position of the common animals of the shore, 

 and is best learnt by repeatedly collecting all the animals 

 found within a given area, say a large pool, and sorting them 

 into their different categories. Such an operation can be 

 readily performed on the shore, and will add greatly to the 

 interest of the early visits to the rocks. It is easy to choose 

 or make a series of little pools which may represent the 

 different classes, then search the rocks in their neighbour- 

 hood, returning after each excursion to the pools to place 

 the spoils in their correct position. At first it is well to 

 have an additional reservoir for. what the naturalist calls 

 incertce sedis. It is not the least of the pleasures of field 

 zoology to find how quickly the eye becomes trained, how 

 the contents of the " uncertainty pool " steadily diminish as 

 the perception of form increases, and the eye picks out 

 perhaps the one obvious point which settles the position of 

 the animal. Errors are of small moment, for after all there 

 is error in the best and most recent classifications. Few 

 years pass in which it is not shown to the scientific world 

 that some form or other, not always an insignificant one, 

 has been assigned to a wrong position, and the best arrange- 

 ment is nothing more than an approximation. The point is 

 to draw up a classification which will as far as may be 

 express your knowledge. If it differs from that adopted by 

 other people, this may be due to your ignorance or to theirs 

 if you but go on you will soon find out which ; it is 

 better to make an error and learn that you are wrong than 

 to accept as dogma a classification which means nothing to 

 you. 



