WHAT IS EOZOON ? 65 



limestone of America. The chalk, which alone 

 attains a maximum thickness of 1000 feet, and, 

 according to Lyell, can be traced across Europe for 

 1100 geographical miles, may be said to be entirely 

 composed of shells of Foraminifera imbedded in a paste 

 of still more minute calcareous bodies, the Coccoliths, 

 which are probably products of marine vegetable life, 

 if not of some animal organism still simpler than the 

 Foraminifera. 



Lastly, we find that in the earlier geological ages 

 there existed much larger Foraminifera than any found 

 in our present seas ; and that these, always sessile on 

 the bottom, grew by the addition of successive chambers, 

 in the same manner with the smaller species. To some 

 of these we shall return in the sequel. In the mean- 

 time we shall see what claims Eozoon has to be in- 

 cluded among them. 



Let us, then, examine the structure of Eozoon, taking 

 a typical specimen, as we find it in the limestone of 

 Grenville or Petite Nation. In such specimens the 

 skeleton of the animal is represented by a white crys- 

 talline marble, the cavities of the cells by green serpen- 

 tine, the mode of whose introduction we shall have to 

 consider in the sequel. The lowest layer of serpentine 

 represents the first gelatinous coat of animal matter 

 which grew upon the bottom, and which, if we could 

 have seen it before any shell was formed upon its 

 surface, must have resembled, in appearance at least, 

 the shapeless coat of living slime found in some portions 

 of the bed of the deep sea, which has received from 



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