198 Notes on “ Inclusions” in Gems, &e. By Isaae Lea. 
The rarity of individuals in a ripe condition in collections may 
be due to their repairing below tide marks at such times, and 
hence avoiding the collector. 
The method above suggested is paralleled in numerous other in- 
vertebrates, and even some fishes, with non-essential differences of 
detail. ‘The specimen referred to has been submitted to several 
naturalists who agree as to the facts. 
While additional evidence is desirable in corroboration, I feel 
tolerably confident of the correctness of the inferences drawn from 
the above facts, which furnish an explanation at once simple and 
in accordance with experience in other cases, of a very puzzling 
question. 
I may add, that the localized turgidity or swelling of the ripe 
seminal ducts had been previously observed by me on other occa- 
sions among specimens of Acmxa patina; but having dissected 
them in most cases from above, removing the membranes not con- 
nected by tissue with the ovary, and looking more particularly for 
a permanent duct or passage, the perforations of the renal mem- 
branes were likely to, and did, entirely escape my notice.—Proceed- 
ings of the Academy of Natural Sciences of Philadelphia. 
V.—Notes on “ Inclusions” in Gems, &e. By Isaac Lua, LL.D. 
In a communication on microscopic crystals contained in gems, 
which the Academy of Sciences of Philadelphia did me the favour 
to publish in its ‘ Proceedings’ * a few years since, I gave some 
figures of these crystals, which I have frequently since verified. I 
then observed that, beside these intercrystalline forms, there were 
in most gems cavities frequently so numerous that they amounted 
to tens of thousands. 
Since the period of the publication of my paper, I have made 
very large additions to my cabinet of gems, and particularly those 
of the Corundum group, sapphires, rubies, and the so-called 
Oriental topaz, Oriental amethyst, Asteria, &c. In the numerous 
fine blue sapphires of my collection, I have rarely explored one 
without finding numerous cavities, and ordinarily also finding the 
beautiful microscopic acicular crystals, which, when the specimen is 
cut cabochon, cause the three bands, and these by crossing form the 
star in Asteria. The cuneate microscopic crystals are also quite 
common. 
Cavities, with or without the fluids, are so frequent in crystals, 
from the soft calcite to the hard corundum, that little may be said 
as to their occurrence, as they are so common. 
* February and May 1869. 
