106 THE MICROSCOPE AND ITS REVELATIONS. 



together, instead of being regularly arranged in layers; the lamellated 

 mode of growth having given place to the acervuline. This change is 

 by no means uncommon among Foraininifera; an irregular piling-together 

 of the chambers being frequently met-with in the later growth of types, 

 whose earlier increase takes place upon some much more definite plan. 

 After what fashion the earliest development of Eozoon took place, we 

 have at present no knowledge whatever; but in a young specimen which 

 has been recently discovered, it is obvious that each successive ' storey' 

 of chambers was limited by the closing-in of the shelly layer at its edges, 

 so as to give to the entire fabric a definite form closely resembling that of 

 a straightened Peneroplis (Plate xv., fig. 5). Thus it is obvious that 

 the chief peculiarity of Eozoon lay in its capacity for indefinite extension ; 

 so that the product of a single germ might attain a size comparable to 

 that of a massive Coral. Now this, it will be observed, is simply due to 

 the fact that its increase by gemmation takes place continuously ; the 

 new segments successively budded-off remaining in connection with the 

 original stock, instead of detaching themselves from it as in Foramini- 

 fera generally. Thus the little GloMgerina forms a shell of which the 

 number of chambers does not usually seem to increase beyond sixteen, 

 any additional segments detaching themselves so as to form separate 

 shells; but by the repetition of this multiplication, the sea-bottom of 

 large areas of the Atlantic Ocean at the present time has come to be cov- 

 ered with accumulations of Gloligerinm, which, if fossilized, would form 

 beds of Limestone not less massive than those which have had their 

 origin in the growth of Eozoon. The difference between the two modes 

 of increase may be compared to the difference between a Plant and 

 a Tree. For in the Plant the individual organism never attains any con- 

 siderable size, its extension by gemmation being limited; though the 

 aggregation of individuals produced by the detachment of its buds (as 

 in a Potato field) may give rise to a mass of vegetation as great as that 

 formed in the largest Tree by the continuous putting forth of new buds. 

 497. It has been hitherto only in the Laurentian Serpentine-Lime- 

 stone of Canada, that Eozoon has presented itself in such a state of pres- 

 ervation as fully to justify the assumption of its Organic nature. But 

 from the greater or less resemblance which is presented to this by Ser- 

 pentine-Limestones occurring in various localities, among strata that seem 

 the Geological equivalents of the Canadian Laurentians, it seems a justifi- 

 able conclusion that this type was very generally diffused in the earlier ages 

 of the Earth's history; and that it had a large (and probably the chief) 

 share in the production of the most ancient Calcareous strata, separat- 

 ing Carbonate of Lime from its solution in Ocean-water, in the same 

 manner as do the Polypes by whose growth Coral-reefs and islands are 

 being upraised at the present time. 



An elaborate work, " Der Bau des Eozoon Canadense" (1878) has been re- 

 cently published by Prof. Mobius of Kiel, in which the structure of Eozoon is 

 compared with that of various types of Foraminifera, and, as it differs from 

 that of every one of them, is affirmed not to be organic at all, but purely Min- 

 eral. Upon this the Author would remark, that if the validity of this mode of 

 reasoning be admitted, any Fossil whose structure does not correspond with that 

 of some existing type, is to be similarly rejected. Thus, the Stromatopora of 

 Silurian and Devonian rocks, which some Palaeontologists regard as a Coral, 

 others as Polyzoary, others as a Calcareous Sponge, and others as Foraminifer, 

 would not be a fossil at all, because it differs from every known living form. 

 Yet the suggestion that it is of Mineral origin would be scouted as absurd by 

 every Palaeontologist. Agai*, it is urged by Prof. Mobius that as the supposed 

 canal-system of Eozoon has not the constancy and regularity of distribution which 



