94 Part III. — Twenty -third Annual Report 



On 29th October 1904 a female cast. It had been isolated a short 

 time before. It was then very limp, and half dead in appearance. It 

 was swollen at the junction of the carapace with the abdomen, and some- 

 what dropsical in appearance. It was not at all smart with its chelae. 



Ehrenbaum says that the lobster merchant is able to distinguish a 

 lobster that is about to cast, by the softening of the ventral edges of the 

 carapace. 



The Cast Shell. 



The colour of the dactyls of the chelae is noticeable. The back edge of 

 the dactyl is clean and purple in colour, and the pores are well marked. 

 The cast stomach is empty. There is a glairy skin under the carapace, 

 and united to the membranous lining of the integument of the abdomen. 

 It ruptures easily, and is often found sticking out as a fold at the junction 

 of the thorax and abdomen Vitzou, who witnessed the moulting of the 

 lobster, describes this skin as a homogeneous, gelatine-like layer, which, 

 under the microscope, shows no cellular structure. It is, he says, a 

 secretion of the lower layers of the new carapace; it passes out by 

 endosmose to lie between the old shell and the new integument. Its 

 presence there facilitates the casting. 



The Soft Lobster. 



The soft lobster, when just cast, is extremely soft and pliable ; the tip 

 of the chela can be made to touch the telson. The stomach is full of 

 little ossicles, which are derived from the breaking-up of the gastroliths. 

 The lobsters at the Laboratory very often failed to rid themselves of 

 their integument. A considerable number died from this cause. 



A lobster that moulted on September 22nd 1902 was kept in one of 

 the compartments of a wooden hatching apparatus until October 14th 

 1902. When in the wooden box it had not eaten food (fish) at all 

 eagerly. It was at the latter date put into a tank, the bottom of which 

 was covered with sand and gravel. It began immediately to eat small 

 pebbles and gravel. Hard lobsters also have been occasionally seen 

 picking up coarse gravel with the pereiopods and putting it into their 

 mouths. 



When a lobster casts in a tank in which there are other lobsters it is 

 usually attacked by them, sometimes before it has finished casting, and 

 it is sometimes fatally injured. A soft lobster occasionally bleeds to 

 death in consequence of what appear to be comparatively slight wounds. 

 On July 15th a lobster was found to have lost both chelae in moulting; 

 it had been attacked and had cast off both claws. One chela was 

 shrivelled just as it is when it is first withdrawn from the shell, and 

 before it has swollen out. The other chela had swollen out to its full 

 size. Both claws were cast off at the fracture plane. Couch observed 

 that " the rejection of the limb can be effected with the same ease 

 while the crust remains soft after exuviation." This fact militates 

 against the view that strong rigid supports are necessary round the 

 fracture plane to permit of the defensive mutilation on the part of the 

 crustacean. 



In another case a hard lobster had lost one chela, and the other bore 

 the scar of a bite. During moulting the scar prevented the withdrawal 

 of this limb, so it was thrown off at the fracture plane. A bud had 

 formed in place of the previously lost limb, and after the cast a diminu- 

 tive chela was present; the hand (propodite and dactylopodite) measured 

 2 1 inches long, while the normal-sized hand measures 4 to 5 inches. Brook 



