DIFFICULTIES AND OP.JKCTIONS 233 



York, Brazil/ and also in those of various parts 

 of Europe, and Dr. Giimbel has found an addi- 

 tional species in rocks succeeding the Laurentian. 



8. The manner in which the structures of Eozoon 

 are effected by the faulting, development of crystals, 

 mineral veins, and other effects of disturbance and 

 metamorphism in the containing rocks, is precisely 

 that which might be expected on the supposition 

 that it is of organic origin. 



9. The exertions of several active and able op- 

 ponents have failed to show how, otherwise than 

 by organic agency, such structures as those of 

 Eozoon can be formed, except on the supposition 

 of pseudo-morphism and replacement, which must 

 be regarded as chemically extravagant, and which 

 would equally impugn the validity of all fossils 

 determined by microscopic structure. In like 

 manner all comparisons of these structures with 

 dendritic and other imitative forms have signally 

 failed, in the opinion of those best qualified to 

 judge. 



Another and perhaps simpler way of putting the 

 case is the following : — Only four general modes of 

 accounting for the existence of Eozoon have been 

 * Fragmental ; specimens from J. A. Derby, Esq. 



