520 foraminifera: — eozoon canadense. 



the lamellated mode of growth having given place to the acervrdine. 

 This change is by no means uncommon among Foraminif era ; 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 deve- 

 lopment of Eozoon took place, we have at present no knowledge what- 

 ever; 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 any single Organism 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 never seems to increase 

 beyond ten, 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 eome to be covered with accumulations of Globigerince, 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 considerable size, its exten- 

 sion 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. 



400. It has been hitherto in the Laurentian Serpentine-Lime- 

 stones of Canada alone, 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 these by Serpentine-Limestones occurring in various 

 localities* among strata that seem the Geological equivalents of the 



* The Author has satisfied himself of this fact, in regard to various 

 specimens of Ophicalcite obtained from various depths in the great Fun- 

 damental Gneiss of Central Europe, the thickness of which Formation is 

 estimated by Sir Roderick Murchison at 90,000 feet ; and the form of 

 Eozoon which there presents itself has been elaborately studied by Prof. 

 Giimbel. (See his Memoir ' Ueber das Vorkommen von Eozoon im ostbayer- 

 ischen Urgeberge,' in the " Sitzungsberichte der Konigl. Acad, der Wis- 

 senschaften in Miinchen," 1866, i, 1). He has also examined with the 

 same result specimens of Serpentine-Limestone, obligingly sent to him 

 by Prof. Loven, of Stockholm, from the Laurentians of Scandinavia. In 



