NATURAL HISTORY OF AMERICAN LOBSTER. 
21 I 
the gastroliths must be dissolved, absorbed into the general circulation, and converted 
into phosphates. There is no reason to suppose that the gastric teeth or any other 
part can make exclusive use of this lime, or use it at all except through the roundabout 
course open to all lime-absorbing cells. Moreover, the total amount of mineral matter 
in the gastroliths is so small that when equally disseminated it is difficult to understand 
how it could be of vital importance. 
It seems altogether more probable that the parts mentioned by Williams are 
hardest in the end because they have the hardest chitinous base in the beginning, and 
that all parts receive only their due proportion of lime. 
Assuming the problem of the gastrolith to be similar in both lobster and crayfish, 
the spicular character of the former may have no special significance. In the crayfish 
these bodies, as we have already seen, are solid stones, which, according to Chantran,® 
are slowly ground down rather than dissolved, their complete dissolution taking upward 
of three days in an adult animal. 
Turning to the other side of the question, the absorption of lime from definite areas 
of the shell is of the utmost importance. Deformity or death awaits every animal in 
which the absorption areas are not duly formed. The production of such areas involves 
the excretion of lime through the medium of the blood. Their actual development 
proceeds, in some measure at least, with the growth of the gastroliths. 
Accordingly, while the question may still be regarded as somewhat involved, we 
still believe that the theory earlier given, that the gastroliths are primarily excreted 
products and represent mineral matter removed from the shell in preparation for molt- 
ing, and that their use for hardening the new shell is purely incidental, is the only one 
which meets all the facts in the case with any degree of success. 
If it could be experimentally shown that the gastrolith is essential to life after the 
molt, as we now know it to be for the safe passage of the molt itself, a theory early 
maintained but not satisfactorily proved, the present status of the question would be 
changed. 
HARDENING OF THE NEW SHELL. 
A lobster which molted while under observation 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 due to the 
turgescence of the tissues. Eighteen hours after shedding 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. 
Another animal which also molted in confinement was kept for a period of 25 
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 
Comptes rendus de 1 ' Academic des sciences, t. lxxvui. Paris, 1874. 
