180 THE DAWN OP LIFE. 



concretions in the same beds, and for their regularity 

 of plan and the delicacy of their structure, and also 

 for minerals of different kinds entering into their 

 composition, and still presenting precisely the same 

 forms and structures. The only remaining theory is 

 that of the filling of cavities by infiltration with 

 serpentine. This accords with the fact that such 

 infiltration by minerals akin to serpentine exists in 

 fossils in later rocks. It also accords with the known 

 aqueous origin of the serpentine nodules and bands, 

 the veins of fibrous serpentine, and the other minerals 

 found filling the cavities of Eozoon. Even the pyr- 

 oxene has been shown by Hunt to exist in the 

 Laurentian in veins of aqueous origin. The only 

 difficulty existing on this view is how a calcite 

 skeleton with such chambers, canals, and tubuli 

 could be formed ; and this is solved by the discovery 

 that all these facts correspond precisely with those to 

 be found in the shells of modern oceanic Foraminifera. 

 The existence then of Eozoon, its structure, and its 

 relations to the containing rocks and minerals being 

 admitted, no rational explanation of its origin seems 

 at present possible other than that advocated in the 

 preceding pages. 



If the reader will now turn to Plate YIII., page 

 207, he will find some interesting illustrations of 

 several very important facts bearing on the above 

 arguments. Fig. 1 represents a portion of a very 

 thin slice of a specimen traversed by veins of fibrous 

 serpentine or chrysotile, and having the calcite of 



