THE AMERICAN LOBSTER. 
93 
a lime reserve, it must be in the lymph, in the form of calcium phosphate, since they 
have no gastroliths. “We think,” they say, “that this theory [of the gastroliths 
contributing to the formation of the new shell] may be dismissed as of comparatively 
little importance, since, even if the teeth and whole calcareous structure could be 
absorbed by the animals, the amount of carbonate of lime at their disposal from this 
source is so small (a very small fraction of the outer covering) that it could not account 
for any considerable part of the new structure. Consequently suck an explanation 
must be abandoned.” 1 
These writers are undoubtedly right in attributing little importance to the gastro- 
liths as a source of lime for the new shell. Lime is usually at hand in abundance in 
the form of the dead skeletons of mollusks and other animals, and, as we have seen 
(see p. 89), young lobsters make free use of it at the time of the molt. The fact that 
the braehyura have no gastroliths should also possess some significance. 
I have already shown that there are considerable areas in the shell where the lime 
is completely absorbed preparatory to the molt. What becomes of the lime thus 
removed ? So far as known, there is no means of eliminating it directly from the body, 
and it is not likely that this amount of lime can be retained in the blood in addition to 
that which the latter is constantly receiving from the food. It seems to me much more 
probable that the gastroliths in the lobster represent the lime which has been removed 
by absorption from the old shell preparatory to the molt, as well as, possibly, a small 
amount which may have entered the blood from the food during the molting period. 
The blood probably contains a maximum quantity of lime at this time, so that very 
little can be absorbed from the food. Upon this hypothesis the absorption of the gas- 
troliths is a purely secondary phenomenon and of comparatively little importance in 
the vital economy. In the braehyura, where no gastroliths are developed, we should 
expect to find the absorption of lime from the shell to be relatively much less, which, 
so far as I can ascertain, is the case. It seems to be a fact also that the absorption of 
lime from the old shell proceeds pari passu with the growth of the gastroliths. 
Chantran observed (see p. 90) that when the formation of the stones was 
arrested in the crayfish the animal died. This might be true of the lobster, and 
would not conflict with the theory proposed. When once formed, the question of the 
subsequent absorption of the gastroliths is not of vital importance. Vitzou speaks 
of a lobster which died six days after the molt, without absorption of the gastroliths 
having occurred. It would, of course, be very illogical to conclude that the gastroliths 
were necessarily in any way concerned with the death of this animal. 
'In an interesting letter from Dr. Irvine, describing some of his recent experiments, he says in 
reference to a former attempt to determine the proportionate quantities of carbonate of lime in the 
exoskeleton: “But as these experiments were made with the common shore crabs, containing much 
less carbonate of lime proportionately to a full grown animal, I have repeated the determination, 
using a full-sized lobster which weighed 15,000 grains. On carefully separating the stomach, and 
freeing it from merely fleshy appendages and drying it, I find it to weigh about 50 grains or of 
the whole animal, while the gastroliths weighed only 20 grains or fhs of the whole.. I then carefully 
dried the outer calcareous structure and found it to weigh 3,720 grains, the proportion between 
the carbonate of lime in the gastroliths and in the outer structure being 20 grains to 3,720 gr ains 
The CaCo;i in the gastroliths thus stood in proportion to the CaCo 3 in the exoskeleton as 1 part in 186, 
an amount too trifling to he of any practical service in providing calcareous matter for it.” 
