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Proceedings of the Royal Irish Academy. 
conclude tliat this hydrous silicate of magnesia filled and enveloped 
the calcareous slvclcton, replacing the perishable sarcode. The 
hypothesis uoay put forward by Messrs. King and liowney to explain 
the ap]X'a]-ances in question, is, that all this curiously arranged serpen- 
tine, Trliich appears to be a cast of the interior of a complex foramini- 
feral organism, has been shaped or sculptured out of plates, prisms, 
and other solids of serpentine, by ''the erosion and incomplete 
waste of the latter, tlie dejiniU shapes being residual portions of the 
solid that have not completely disappeared." The calcite which 
limits tliese definite shapes, or, in other words, what is regarded as the 
calcareous skeleton of Eozoon, is a '' replacement pseudomorph" of 
calcite taking the place of the wasted and eroded serpentine. It was 
not a calcareous fossil, filled and surrounded by the serpentine, but 
was formed in the midst of the serpentine itself, by a mysterious 
agency which dissolved away this mineral to form a mould, in which 
the calcite was cast. Tliis marvellous process can only be paralleled 
by the operations of that plastic force in virtue of which sea-shells 
were supposed by some old naturalists to be generated in the midst of 
rocky strata. Such equivocally formed fossils, whether oyster or 
foraminifers, may well be termed pseudomorphs, but we are at a loss 
to see with what propriety the authors of this singular hypothesis 
invoke the doctrines of mineral pseudomorphism, as taught by Eose, 
Elum, Bischof, and Dana. In replacement pseudomorphs, as under- 
stood by these authors, a mineral species disappears and is replaced by 
another which retains the external form of the first. Could it be 
shown that the calcite of the cell-wall of Eozoon was once serpentine, 
this portion of carbonate of lime would be a replacement pseudomorph 
after serpentine ; but why the portions of this mineral, which in the 
hypothesis of Messrs. King and Rowney have been thus replaced, 
should assume the forms of a foraminiferal skeleton, is precisely what 
our authors fail to show, and, as all must see, is the gist of the whole 
matter. 
Messrs. King and Eowney, it will be observed, assume the exist- 
ence of calcite as a replacement pseudomorph after serpentine, 
but give no evidence of the possibility of such pseudomorphs. Both 
Hose and Bischof regard serpentine itself as, in all cases, of 
pseudomorphous origin, and as the last result of the changes of a 
number of mineral species, but give us no example of the pseudo- 
morphous alteration of serpentine itself. It is, according to Bischof, 
the very insolubility and unalterability of serpentine which causes it 
to appear as the final result of the change of so many mineral species. 
Delesse, moreover, in his carefully prepared table of pseudomorphous 
minerals, in which he has resumed the results of his own and all 
preceding observers, does not admit the pseudomorphic replacement of 
serpentine by calcite, nor indeed by any other species.^ If, then, 
* *' Annales des Mines," 5, xvi. 317> 
