200 THE DAWN OF LIFE. 



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. This 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 oysters or Foraminifers, may well be 

 termed pseudormorphs, but we are at a loss to see with what 

 propriety the authors of this singular hypothesis invoke the 

 doctrines of mineral pseudormorphism, as taught by Rose, 

 Blum, Bischof, and Dana. In replacement pseudomorphs, as 

 understood 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 on 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 Rowney, it will be observed, assume the 

 existence of calcite as a replacement pseudomorph after serpen- 

 tine, but give no evidence of the possibility of such pseudo- 

 morphs. Both Rose 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 pseudomorphous alteration of serpentine 

 itself. It is, according to Bischof, the very insolubility and 

 unalterability of serpentine which cause 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 re- 

 placement of serpentine by calcite, nor indeed by any other 



