188 THE DAWN OP LIFE. 



"21st. The occurrence of ' eozoonal features' solely in crystal- 

 line or metamorphosed rocks, belonging to the Laurentian, 

 the Lower Silurian, and the Liassic systems never in ordinary 

 unaltered deposits of these and the intermediate systems 

 must be assumed as completely demonstrating their purely 

 mineral origin." 



The answers already given to these objections may be 

 summed up severally as follows : 



1st. This is a mere hypothesis to account for the forms pre- 

 sented by serpentine grains and by Eozoon. Hunt has shown 

 that it is untenable chemically, and has completely exploded it 

 in his recent papers on Chemistry and Geology.* My own 

 observations show that it does not acccord with the mode of 

 occurrence of serpentine in the Laurentian limestones of 

 Canada. 



2nd. Some of the things stated to parallel the intermediate 

 skeleton of Eozoon, are probably themselves examples of that 

 skeleton. Others have been shown to have no resemblance 

 to it. 



3rd. The words "more or less " indicate the precise value of 

 this statement, in a question of comparison between mineral 

 and organic structures. So the prismatic structure of satin- 

 spar may be said " more or less " to resemble that of a shell, 

 or of the cells of a Stenopora. 



4th. This overlooks the filling of chamber casts with py- 

 roxene, dolomite, or limestone. Even in the case ofloganite 

 this objection is of no value unless it can be applied equally 

 to the similar silicates which fill cavities of fossils f in the 

 Silurian limestones and in the greensand. 



5th. Dr. Gumbel's observations are those of a highly skilled 

 and accurate observer. Even if crystalline forms appear in 

 " chamber casts," this is as likely to be a result of the injury 

 of organic structures by crystallization, as of the partial efface- 

 ment of crystals by other actions. Crystalline faces occur 

 abundantly in many undoubted fossil woods and corals ; and 



* Boston, 1874. 



t See for a full discussion of this subject Dr. Hunt's " Papers " 

 above referred to. 



