vi MACRURA NEI'HROPSIDEA LOBSTER 155 



dangerous one to the Lobster and to Crustacea in general, and is 

 very frequently fatal. There is, first of all, the danger of the act 

 not being accomplished skilfully, when death always ensues. 

 The Lobster remains soft and unprotected for about six weeks 

 after the ecdysis, and is very apt to fall a prey to the predaceous 

 fish, such as Sharks, Skates, Cod, etc., which feed upon it. 

 There are, however, some peculiar adaptations connected with the 

 process which are of interest. In order to facilitate the ecdysis, 

 areas of absorption are formed upon the dorsal and ventral 

 surfaces of the carapace, on the narrower parts of the chelipedes, 

 and at other places ; in these areas the calcium carbonate is 

 absorbed, and the old shell becomes elastic and thin, so as to 

 allow a more easy escape for the moulting Lobster. It has been 

 noticed that while this is taking place large concretions of 

 calcium carbonate are formed at the sides of the stomach, known 

 as " gastroliths," which perhaps represent the waste lime that 

 has been abstracted from the areas of absorption. After 

 moulting the Lobster is in great need of lime for stiffening his 

 shell, and it has been noticed that on these occasions he is very 

 greedy of this substance, even devouring his own cast-off skin. 



The male Lobster is especially prized on account of his 

 larger chelae, but in both sexes the chelipedes are differentiated 

 into a smaller cutting pincer and a larger crushing one. Lobsters 

 may be right or left handed, with the large crushing claw on the 

 right or left hand, and sometimes specimens occur with the 

 smaller cutting pincers on both chelipedes, and very rarely, 

 indeed, with crushing claws on both sides. Crustacea very 

 commonly have the power of casting off a limb if they are 

 seized by it or if it is injured, and of regenerating a new one. 

 In the Lobster a so-called breaking-joint is situated on each leg 

 at the suture between the fused second and third segments ; 

 a membrane being pushed inwards from the skin, which not 

 only serves to form a weak joint where rupture may easily take 

 place, but also to stop excessive bleeding after rupture. In the 

 newly-hatched larvae there is a normal joint between the second 

 and third segments; and autotomy, or the voluntary throwing away 

 of a limb, never occurs until the fourth larval stage, when the 

 breaking joint is formed. Autotomy is a reflex act under the 

 control of the segmental ganglion ; if a Crab or Lobster be 

 anaesthetised, and then a limb be injured or broken off below the 



