at great depths in the Sea. 31 
On mounting the shells acted on in the latter mode, some in 
balsam, some dry, all depolarizing effect was destroyed, there 
being no coloration in a single specimen; whilst all trace was 
obliterated of the remarkable and distinctive black cross ordi- 
narily presented by Globigerine when viewed under the polari- 
scope. On the other hand, the micaceous tablets retained their 
full depolarizing properties, and evolved the most brilliant colour. 
Again, the bodies detected by me in the deep-sea deposits 
and which I denominated Coccospheres *, as indicative of their 
relation to the Coccoliths of Professor Huxley, though abundantly 
present in the material operated on, were not destroyed by the 
cold acid. But the minute black crosses which they evoke when 
observed under the polariscope were, in like manner with that 
of the perfect Globigerina-shells, wholly obliterated. 
In a few shells a change of crystalline structure appeared to 
have taken place, inasmuch as the bold conical elevations 
already referred to were replaced by crystals of the cubical 
series, resembling in all respects the natural crystals of the 
fluoride of calcium. Accordingly, it is probable that, notwith- 
standing the transitory period of their immersion, the carbonic 
was replaced by fluoric acid, and the peculiar depolarizing power 
resident in the normal arrangement of particles destroyed. 
On the other hand, it is possible, although hardly probable, 
that an entirely new combination, dependent on alterations 
induced in the sarcodic matter with which the Glodigerina-shells 
and, I believe, the Coccospheres and Coccoliths are, in a measure, 
invested, may have exercised a similar action as regards depolar- 
ization. 
At all events, we are here furnished with a new and simple 
method of testing microscopically for carbonate of lime—a salt 
which enters largely into the composition of so many marine 
and other deposits, and is associated with so many of the minute 
organisms that frequent both salt and fresh water. 
My own time being already fully occupied, I must leave the 
further investigation of the matter to others. Perhaps I may 
be permitted to remark that no one is more competent to extract 
the true significance of the fact than Mr. Sorby, whose researches 
on Pseudomorphs are so well known. 
Meanwhile, may I request you will do me the favour to insert 
this notice in ‘The Annals?’ 
I remain, Gentlemen, 
Your obedient and obliged servant, 
G. C. Watticu. 
* See a notice by me in the Ann. & Mag. of Nat. Hist. No. 43 (ser. 3. 
vol. viii.), and the article on the so-called Crystalloids of the Chalk, by 
Mr. Sorby, in No, 45, 
