842 MICKOSCOPIC FORMS OF ANIMAL LIFE 



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. 

 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 Foraminifera generally. Thus 

 the little Globigerina 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 covered with 

 accumulations of Globigerince, which, if fossilised, 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 herb and a 

 tree. For in the herb the individual organism never attains any 

 considerable 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. 



It has been hitherto only in the Laurentian serpentine lime- 

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

 preservation as fully to justify the assumption of its organic nature. 

 But from the greater or less resemblance which is presented to this 

 by serpentine-limestones occurring in various localities among strata 

 that seem the geological equivalents of the Canadian Laurentians, it 

 seems a justifiable conclusion that this type was very generally dif- 

 fused 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, separating carbonate of lime from its solu- 

 tion 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 recently published by Professor Mb'bius, 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 mineral. 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 Stroma- 

 topora of Silurian and Devonian rocks, which some palaeontologists 

 regard as a coral, others as polyzoary, others as a calcareous sponge, 

 and others as a foraminifer, would not be a fossil at all, because it 



