of the Fishery Board for Scotland. 



93 



The Hardening of the Shell. 



The shells of the soft lobsters hardened only very slowly, in this 

 respect differing from cases reported by other observers. A male lobster 

 that cast when in a box floating in Dunbar harbour in July 1902 was 

 33 days later hard. It had lost nearly all its pereiopods, and so had 

 difficulty in walking. It arrived at the Laboratory on September 30th, 

 and lived there until December 30th 1902. Herrick says that six to eight 

 weeks are required to complete the hardening process, a period also 

 given by Prince. Ehrenbaum gives a period of from three to four 

 weeks. Meek records a lobster that, having cast on September 12th, 

 regained its hardness of shell in one month. 



The lobsters in the Laboratory were not eager for food immediately 

 after the moult. The food was shelled mussels usually, with fish 

 occasionally. The integument, once it became stiffened, remained for a 

 long time more or less pliable, as if the calcified layer of the shell were 

 poorly developed. Whether the slow hardening is due to the nature of 

 the food or of the sea-water is not known. The shells, many months 

 after the cast, were deficient in lime and cut easily like brown paper. 



The lobster that cast on September 22nd 1902 was still soft to the 

 extent that the intsgument is flexible and yields to pressure, when it 

 died, viz. on June 6th 1903. Another which cast about the middle of 

 August was fairly hard a fortnight later. Three lobsters which moulted 

 in July 1903, and one that moulted in August of the same year, were in 

 the following July 1904 still softish in the shell. They were in good 

 condition, for two of them cast during that month. The fact, then, that 

 their shells had not become as hard as that of the lobsters caught in the 

 sea, did not apparently constitute any weakness in the animals. 



A female which cast on 19th October 1903 was fairly hard on December 

 30th 1903. One of the casters of 1904 was kept until April 2nd 1905, 

 when it was found dead. It was fairly hard, but the carapaces and 

 integument of the abdomen cut easily with a knife. On the shell there 

 was a considerable number of the shells of an annelid. The colour of 

 the carapace was a dull black. It is possible that the food supply is not 

 sufficiently varied to supply all the materials necessary for the building- 

 up of the shell. 



One of the lobsters that cast in July 1903 was on October 21st 1904 

 not very hard. It was found dead on February 17th 1905, and it was 

 then hard. 



A female lobster cast in July 1904; on May 6th 1905 it was still 

 rather soft. 



The shell of a soft lobster, when put into alcohol, turns red ; the colour 

 of the hard shell— blue-black — is not affected by the alcohol. 



Indications of Approaching Moulting. 



When the stock of lobsters was examined on 21st October 1904 one of 

 the lobsters, a female, that had hatched its eggs a month or two previously, 

 attracted attention. The carapace was raised posteriorly and separated a 

 little from the first abdominal joint ; the skin between the carapace and 

 the abdomen was bulged out. Ventrally the soft parts between the abdo- 

 minal segments were turgid. The absorption areas on the chela were a 

 deep bright blue, and yielded a good deal to pressure, showing that 

 absorption of the calcarevms layer had been going on there. The lobster 

 was separated from the others, and it cast on November 1st. 



G 



