MARINE CRUSTACEA IN CONFINEMENT. 55 



specimen one claw is rather more than twice the length of the 

 other, and it is, I think, analogous to the crippled wing of a moth. 

 It is well known that such a slight cause as the sticking of a piece 

 of the chrysalis-shell will hinder the development of the wing, 

 and if its growth be arrested it will never expand to its full size, 

 for the soft ductile substance of the wing is in an incredibly 

 short time acted on by the gases of atmospheric air, known or 

 unknown, and converted into chitine and membrane. Some- 

 thing similar goes on in the case of the shell of a Crab. At 

 first it is quite soft, with apparently no more substantiality 

 than the body of a jelly-fish, if so much. It is just a sort of 

 gelatinous slime, which subsequently becomes like a double mem- 

 brane, enclosing water or gelatinous slime between it. Then 

 changes ensue so rapidly that I have never been able to follow 

 them with the microscope. 



I had, some little time ago, the idea of making a combination 

 of microscope and cinematograph camera, and then examining 

 the long strip of film in detail. I greatly regret I was unable to 

 afford the outlay, as I believe much might be learned by this 

 means about processes too rapid for investigation with unaided 

 vision. 



Carcinus mcenas lives ten years and more I know, but how 

 much longer I am unable to say from personal observation. 

 A Crab ten years old has exuviated for the last time, and done 

 growing. Its shell has become a resting-place for barnacles, 

 and possibly seaweeds may be growing thereon. A patriarchal 

 Crab I had died last spring, killed by a frosty night ; its shell 

 was covered with acorn barnacles, which seemed to enjoy being 

 carried about, now in and now out of the water. 



The Shore Crabs do not seem to be able to stand very cold 

 weather, and I have lost many I had hoped to have kept to 

 extreme old age. They bury themselves in the sand as soon as 

 the temperature falls below forty degrees, and would retreat into 

 deep water if they could. 



The Edible Crab is far inferior to the Shore Crab in intelli- 

 gence, and not so easily tamed ; but it is not particularly difficult 

 to keep in captivity if one feeds it carefully. It is not happy 

 unless it has stones to hide under, and most of its time seems to 

 be spent asleep. It is the longest lived Crab I am acquainted 



