420 TEXT-BOOK OF ZOOLOGY 



Hiding-places of this kind, however, are only to be found on a rocky 

 bottom, and hence the lobster only frequents those parts of the sea 

 where the bottom is of this nature, to the colour of which, moreover, 

 that of the animal closely assimilates. 



A very similar species, the Spiny Lobster (Palinurus vulgaris), is 

 found from the Mediterranean to the south-west coast of England. This 

 animal is unprovided with prehensile weapons (no pincers are developed 

 on the legs). Its only protection against hostile attacks consists in its 

 strong spine-covered shell. 



The Shrimps are small marine crustaceans, which, after being boiled, 

 are sent considerable distances inland. By their colour alone we can 

 separate them into two distinct species, viz., the Prawns (Palfemon 

 serratus), which are of a bright red colour after boiling, and a grayer 

 kind, the Common Shrimps (Crangon vulgaris), whose colour even 

 after boiling is little different from that which during life hid them 

 from the view of their enemies on the sandy bottom. Their long 

 abdomen, the large abdominal legs, which are used as oars (" swim- 

 merets "), and the long tail fin, all point out these animals as excellent 

 swimmers. 



On the other hand, the adults of the Hermit Crab (Pagurida) are 

 totally incapable of swimming, for their swimming organ, the abdomen, 

 is so soft that the animal is obliged to use a mollusc shell for its 

 protection, and thus becomes a " hermit" (name). The animal crawls 

 backwards into this alien dwelling, which it only abandons when the 

 shell is too small for it, i.e., when its body has grown too large for its 

 house. The crab is then obliged to exchange it for another roomier 

 one. The animals retain hold of their dwelling by means of their 

 terminal abdominal appendages, which have been modified into clasping 

 organs, and the two last thoracic legs. Only the hard-shelled portions 

 of the body and the eyes on their long peduncles protrude from the 

 shell. Protected by this strong castle, the animal goeu in pursuit of 

 prey, and on the approach of any danger withdraws as far as possible 

 into its fortress, the entrance to which is barred by one of the two claws, 

 which for this reason is much larger than the other. Some species of 

 these peculiar crustaceans further protect themselves by contracting a 

 kind of "friendly alliance" with certain sea-anemones (which see), 

 particular species of the latter being regularly found on the shells 

 occupied by the hermit crab ; and it has been stated that when the 

 latter enters a new dwelling it carefully with its claws removes the 

 anemone from the old house and transplants it to the new one. Placed 

 under the protection of the stinging "nettle threads" of the anemone, 

 which are carefully avoided by all sensitive animals, the hermit crab is 



