204 LIFE BY THE SEASHORE. 



associated with their differences in habit and mode of life. 

 The intimate nature of the association is often easier to 

 demonstrate in the Crustacea than in other groups, and 

 adds much of their interest to them. 



Though the chapters on the Decapod Crustacea have 

 spun themselves out to an unreasonable length, it is not 

 easy to tear ourselves away from so fascinating a group. 

 Two subjects have not yet been spoken of, and must just 

 be touched on. 



One of these is the moult, too interesting a phenomenon 

 of Crustacean life to be omitted. We have already dwelt 

 upon the characteristic Crustacean cuticle, or coat, and its 

 advantages as a defence. It has, however, the correlated 

 disadvantage that it periodically becomes too small for its 

 owner, and has to be cast and renewed. This occurs in all 

 Crustacea, but is perhaps best and most frequently seen in 

 the edible crab. If you search diligently under stones far 

 out on the rocks, you will certainly sooner or later come 

 across an edible crab in a sluggish apathetic condition. 

 Watch it, and you will see the whole of the shell split off 

 at the insertion of the legs, and thrown aside, snowing 

 beneath it the new coat, very bright in colour but perfectly 

 soft to the touch. Little by little the crab also extricates 

 himself from the rest of his coat, pulling his claws slowly 

 from their envelope, and gradually pushing the discarded 

 shell away from him. Pick this up, and you will find that 

 it is complete in every detail; not only is the covering of 

 every appendage (even the most minute) fully represented, 

 but the covering of the eyes, of the gills, nay, even the 

 lining of the stomach is there. Turn to your soft, helpless 

 crab, and you will see a stranger sight still : the crab which 

 has just come out of the shell you hold in your hand is 

 now bigger, is probably what will seem to you very much 

 bigger than that shell. If, as one is often very apt to do, 

 you have placed the crab when first seen in a bottle for 

 transport, you will find that what went in easily will by no 

 means come out without injury. The meaning of which 

 strange fact is that as the new coat does not stay soft for 

 long, the crab must hasten to get all the growing- done 

 possible in the short time at its disposal. But growth is 

 a slow process, so it distends its tissues with water to en- 



