92 ESSENTIALS OF ZOOLOGY 



and it is obtained as far south as the Mediterranean. Unlike 

 its ally, the common lobster, it occupies soft or muddy ground. 

 Norway lobsters are caught by trawlers at all seasons, and 

 may be obtained at most of the markets. 

 ,7': At a glance it is seen to be very like the common lobster 

 and the crayfish and other long-tailed Decapod Crustaceans. 

 Like these, moreover, it crawls by the action of the walking 

 legs forwards and backwards, and shares with many of them 

 the power of swimming backwards at a very rapid rate by 

 strong, rapid contractions of the abdomen. The force exerted 

 may be estimated when the living animal is held in the hand. 

 The diet is almost, if not quite, a purely animal one. The 

 food is seized by the long pincers, or chelae, and conveyed by 

 the foot-jaws or maxillipeds to the mouth. 



Growth takes place by a series of ecdyses or moultings, 

 but it has been observed exceptionally that ecdyses may 

 occur without growth apparently resulting. At each ecdysis 

 the whole of the cuticle and the parts internally continuous 

 with it are thrown off or ' cast.' The ecdyses occur very 

 frequently at the beginning of growth, and then also more 

 frequently in the summer than in the winter ; but the periods, 

 called instars, between them become more and more ex- 

 tended, concomitant with the slowing down in the intensity of 

 growth, which ceases when the animal reaches a size of some 

 eight to ten inches. The limit of size, however, is not quite 

 the same in every locality, and may vary, indeed, in the same 

 locality. 



All the appendages may be regenerated when lost, and the 

 pereiopoda may be automatically thrown off at the ' breaking 

 joint ' near the base of the limb. 1 



As a rule, the external cuticle of the Norway lobster is not 

 much subject to the commensal attachment of other animals, 

 but in some cases certain zoophytes obtain a lodgment. 



EXTERNAL MORPHOLOGY. The body, which is light red in 

 colour, is divided into a cephalothorax and an abdomen, each 

 with a definite number of appendages. The head consists of 

 five segments, the thorax of eight segments, and the abdomen 



1 1915. Paul, Autotomy among the Decapod Crustacea, Report, Dove 

 Marine Laboratory. New Series, IV. 



