90 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
gastroliths may liave no significance in these cases, but in order to determine this 
one should examine the stomachs of larger animals which have recently molted under 
natural conditions. 
The gastroliths, though a part of the cuticle, are not cast off during the molt, but 
are retained in the stomach. When the old lining of this organ is withdrawn, the 
gastroliths are soon set free, and breaking up into their constituent parts are speedily 
dissolved. 
In the lobster referred to above (No. 2, table 24), which was preserved immediately 
after the old shell was shed, the gastroliths were still in place in the stomach, and 
unchanged. (For chemical analysis of these, see table, Appendix II, No. 4 a.) The 
horny parts of the gastric ossicles agree closely will) those of the cast shell, having 
the same light-brown color and approximately the same hardness. The supporting 
calcareous parts are, however, quite soft. In every case which I have examined, the 
old teeth are expelled from the stomach at the time of ecdysis, and not left with the 
gastroliths, as Beaumur (161) said was true of the crayfish. 
Experiments upon the crayfish have seemed to show that the gastroliths are 
necessary for the hardening of the new shell, but this is undoubtedly an error. 
The length of time required for the development of the gastroliths of the lobster 
has not been determined. It is probable, however, that the latter part of their devel- 
opment is rapid, and that they are conspicuous objects for a few days only before the 
shell is cast off. 
A female lobster which was examined August 10, 3893, had a very hard, dull- 
colored shell, which one might infer would be shed before many weeks. In place of 
the gastrolith there was a very thin gastrolithic plate in the lateral wall of the stomach 
(fig. 183, pi. 44). A section through this plate (fig. 171, pi. 43) shows how the gastrolith 
is developed. The cuticular epithelium is columnar, consisting of very long, slender 
cells. The thick excreted cuticular product is traversed by undulatory striations, 
which mark off the columnar ossicles, the separation of which begins at the outer 
surface. 
The inner section of the gastrolithic plate (G P) appears much more homogeneous 
than the outer portion, although the demarcation is not quite so sharp as appears in 
the figure. The striations in the inner part are only conventionally represented. The 
undulatory striae extend inward, and with the deposition of lime the ossicles are 
developed and completely separated. When the gastroliths are fully formed (cut 9, 
plate 0) the deciduous cuticle of the gastrolithic sac is differentia ted into two parts, 
the gastrolith (gg) and a thin outer layer (oc\ cuts 9 and 10) corresponding to the 
outermost part of the cuticle shown in figure 171 and in continuity with the old lining 
of the stomach (Old C). The new cuticle of the stomach (New C) is represented in 
the gastrolithic sac by a thin stratified layer (nc\ cuts 9, 11), from which the next 
gastrolith will be developed. 
The condition of the gastrolith at this stage bears a resemblance to that which is 
finally reached in the crayfish, where, according to Huxley (103) : 
It is a solid body which, in vertical section, is seen to be composed of thin superimposed layers, 
the densest of which form the hard projections of the outer surface next the epithelial substratum. 
The outer side of the gastrolith in the crayfish is roughened with irregular promi- 
nences, so that it resembles a a brainstone v coral. When from any cause the stones 
arenot dissolved, they lose their normal blue or white color and become brown or green ; 
the shell remains soft and the animal, according to Chantran, soon dies. When the 
