Crabs, Lobsters, Shrimps, Barnacles, etc. (Crustacea). 



animals capable of producing sounds: the friction of the basal 

 joint of the antenna against the carapace produces a grating noise. 



An alhed kind is the Flat-lobster, Scyllarus latus (fig. 46), 

 a clumsy animal which spends the greater part of its life in some 

 crevice of the rock. Its broad back is generally covered with mud 

 and brown alg^e, and is often mistaken for a stone. It uses its 

 front pair of feelers, shaped like two broad shovels, as weapons 

 of defence; and whilst feeding it covers its food with them. In 

 tank Nr. 23 the Lesser Flat-lobster, Scyllarus arctus, is often to be 

 found; a more brilliantly coloured and livelier fellow. 



Of the smaller long-tailed kinds we would mention the Shrimps 

 and Prawns, such as Crangon and Palaemon (fig. 145), remarkable 

 for their lively jumping. They inhabit all the rocky coasts in 

 large numbers, and are the staple food of many animals : in tanks 

 Nr. 20 and 23 of the Aquarium they are largely used for feeding 

 purposes. Their movements when walking or swimming are easy 

 and graceful, and they are so sensitive that they feel the least 

 disturbance of the water and respond to it by tremendous leaps. 



Two rare Shrimps, not always present in the Aquarium, are 

 Stenopus (fig. 131), and Penaeus (fig. 132). The latter is exceed- 

 ingly palatable, and, as it has a very thin skin, would be very 

 valuable as an article of food if it were only a little more common. 

 In the Bay of Gaeta it is largely caught under the name of "mazza- 

 cuogno". 



We now turn to a curious group intermediate between the 

 long-tailed Lobsters and Shrimps, and the short-tailed Crabs. To 

 this group belongs the beautiful Galathea (red with blue stripes; 

 tank 23) but more especially the Hermii-crabs or Pagurids (figs. 143 

 and 144). 



A whelk-shell walking about on crab's legs and carrying sea- 

 anemones on its back — such is the impression made on anyone 

 looking for the first time at a Hermit-crab (tank Nr. 23). This 

 droll figure fascinates us at once and creates in us a desire to know 

 something more about it. The problem is simpler than it seems, 

 and has the following explanation. The Hermit-crabs live in de- 

 serted whelk-shells. When they escape from the egg they are 

 just like the young long-tailed prawns; but very soon their pre- 

 viously straight tail begins to twist itself spirally, and the time 

 has come for the small animal, which is scarcely half an inch 

 long, to look out for a shell. If it finds an empty one suitable for 

 its size, it puts its tail into it ; but if it does not, it first eats out the 

 whelk and then takes possession of the shell. In the course of 

 many generations the hind portion of the body has become so ac- 

 customed to a borrowed covering that it is quite soft, and re- 

 sembles an unjointed sack (fig. 162) possessing at its extremity 

 a pair of rudimentary legs ; with these it holds so fast to the shell, 

 that in trying to extricate the animal you may very often tear 



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