THE AMERICAN LOBSTER. 95 



According to the researches of Irvine and Woodhead lime salts, in whatever con- 

 dition absorbed, are changed daring digestion into acid phosphates, and in this state 

 are carried by the blood to the protoplasm of the chitinogenous cells. The nascent 

 carbon dioxide gas, which the active protoplasm of these cells throws off, precipitates 

 calcium carbonate (CaC0 3 ) and calcium phosphate (Oa 3 (PO.,),>). These salts are then 

 dialyzed into the dead chitinous matrix, where they are finally laid down. Lime is 

 deposited in an insoluble condition only in vitally inactive tissues. They found that 

 crabs which began to shed late in the season were retarded by the cold. Heat tlms 

 seems to be a necessary factor in the assimilation of lime salts from seawater by these 

 animals. They also found that the crabs died in watercontaining only sodium chloride 

 (NaOl), but lived without molting in water containing NaCl and magnesium chloride 

 (MgCl 2 ); they lived and molted in water which contained NaCl, MgCl 2 , and calcium 

 chloride (CaCl 2 ), the latter in the amount equivalent to the lime in normal sea water. 



A lobster which molted while under observation (No. 7, table 24) was watched 

 particularly with reference to the hardening of the shell. One hour after the molt 

 the cuticle seemed to the touch of the finger to be perceptibly hardened, but this may 

 have been partially due to the turgescence of the tissues. Eighteen hours after shed- 

 ding the cuticle had a leathery consistency, and the tubercles and spines had hardened 

 slightly. The shape of all the parts was perfectly normal. Four days after the molt, 

 when the animal died, the cuticle was still coriaceous, and but slight increase in the 

 stiffness of any parts had occurred. 



A lobster which also molted in confinement (No. 6, table 24) was kept for a period 

 of twenty-five days. The carapace at the end of this time was easily compressible 

 between the thumb and finger. The large claws could be made to yield in the same 

 way, but not without using considerable force. It was in the state which the fisher- 

 men call "paper shell" or " rubber shell." If sent to market it would be classed as a 

 soft-shell lobster. It is possible, of course, that in this space of time a lobster under 

 natural conditions would have become harder. It is safe to conclude, However, that 

 from six to eight weeks are necessary, under ordinary conditions, to produce a shell 

 which is as hard as that cast off; and if the lobsters were destined for the market they 

 would probably be in a still better condition in ten weeks or three months. Many 

 lobsters are caught and shipped to dealers a few weeks after they have molted, but 

 their meat is then soft and of inferior quality, as we have already remarked. According 

 to the opinion of a canner of lobsters in Maine, 7 pounds of soft-shelled lobsters in 

 summer or fall will yield no more than 4 pounds in spring, when the flesh is more solid. 



Eeaumur says of the crayfish (162) that he has seen the new shell become as hard 

 as the old in 24 hours, but that it usually takes from two to three days. This observa- 

 tion is confirmed by Chantrau (37), who says: 



Twelve hours after the molt, the nippers are already hard enough to pinch sharply, and in 24 

 hours they are completely hardened. The sides of the back remain flexible for a much longer time, 

 but at the end of 48 hours they have attained a degree of consistency which is almost normal. 



Vitzou remarks that the carapace of the crabs has perceptibly hardened after 24 

 hours, but is not completely hardened until after 72 to 80 hours. 



It has been stated that the shell of the newly molted lobster becomes as hard as 

 formerly in the space of 24 hours. This and many similar conjectures which have 

 been made upon this subject are entirely erroneous, as proved by the statistics of the 

 fishery during the summer months. It is probable, however, that under exceptional 

 conditions this process is subject to much variation. 



