SHRIMPS, CRABS, AND BARNACLES 101 



was allowed to be eaten by good Catholics on fast days ! 

 Two hundred years or more ago this story was dis- 

 credited by serious naturalists, but the barnacles and sea- 

 acorns were thought (even by the great Cuvier) to be 

 of the nature of oysters, mussels, and clams (Molluscs), 

 because of their possessing white hard shells in the form 

 of " valves " and plates, which can open and shut like those 

 of mussels. Their true history and nature were shown 

 about eighty years ago by a great discoverer of new 

 things concerning marine creatures, Dr. Vaughan 

 Thompson, who was Army Medical Inspector at Cork, 

 and studied these and other animals found in the waters 

 of Queenstown Harbour. 



The crab class, or Crustacea, have, like the insects, 

 centipedes, spiders, and scorpions, a body built up of 

 successive rings or segments. The earth-worms (as every 

 one knows) and marine bristle-bearing worms also show 

 this feature in the simplest and most obvious way. The 

 vertebrates, with their series of vertebrae or backbone- 

 pieces and the body muscles attached ring-wise to them, 

 show the same condition. The marine worms have 

 a soft skin and a pair of soft paddle-like legs upon 

 each ring of the body, often to the number of a hundred 

 such pairs. But the crab class and the classes called 

 insects, centipedes, arachnids, and millipedes are remark- 

 able for the hard, firm skin, or " cuticle," which is formed 

 on the surface of their bodies and of their legs, which, as 

 in the marine worms, are present — a pair to each body- 

 ring or segment — often along the whole length of the 

 body as in centipedes. This hard cuticle is impreg- 

 nated with lime in the bigger members of the crab 

 class, such as the lobster. It is not equally thick and 

 hard all over the surface of the lobster, but is separated 

 by narrow bands of thin, soft cuticle into a number of 



