THE BEGINNING OF LIFE ON THE EARTH. 29 



resisting than the limestone, they project when weathered, or 

 when the limestone is etched by an acid, so as to show the 

 lamination very distinctly. At the lower surface of the masses 

 the layers are seen to be thicker than they are above, and in 

 perfect specimens they are seen toward the surface to break up 



Fig. 16. — Nature-printed specimen of Eozocn slightly etched with acid. It shows the 

 lamination, and at one side fragmental Eozoon {Life's Daivn on Earth). 



into small rounded vesicles of calcite, like little bubbles, which 

 constitute the so-called acervuline condition of Eozoon (Fig. 

 15, No. 2). Slices of the fossil etched with an acid show 

 these appearances very perfectly, and can even be printed 

 from, so as to present perfect nature-prints of the structure 

 (Fig. 16). 



On etching a small fragment or slice with very dilute acid, 



