M. Otto Hahn on Eozoon canadense. 267 



beds are found in many parts to contain masses of considerable 

 size, but usually of indeterminate form, disposed after the 

 manner of an ancient coral-reef, and consisting of alternating 

 layers — frequently numbering more i\\?in fifty — of carbonate of 

 lime and serpentine (silicate of magnesia). The regularity of 

 this alternation, and the fact that it presents itself also between 

 other calcareous and siliceous minerals, having led to a suspi- 

 cion that it had its origin in organic structure, thin sections of 

 well-preserved specimens were submitted to microscopic ex- 

 amination by Dr. Dawson of Montreal, who at once recognized 

 its Foraminiferal nature *; the calcareous layers presenting the 

 characteristic appearances of true shelly so disposed as to form 

 an irregularly chambered structure, and frequently traversed 

 by systems of ramifying canals corresponding to those of Gal- 

 carina ; whilst the serpentinous or other siliceous layers were 

 regarded by him as having been formed by the infiltration of 

 silicates in solution into the cavities originally occupied by 

 the sarcode-body of the animal, — a process of whose occurrence ' 

 at various geological periods, and also at the present time, 

 abundant evidence has already been adduced. Although this 

 determination has been called in question, on the ground that 

 some resemblance to the supposed organic structure of Eozoon 

 is presented by bodies of purely mineral origin f, yet, as it has 

 not only been accepted by all those whose knowledge of Fora- 

 miniferal structure gives weight to their judgment, but has 

 been fully confirmed by subsequent discoveries |, the author 

 feels justified in here describing Eozoon as he believes it to 

 have existed when it originally extended itself as an animal 

 growth over vast areas of the sea-bottom in the Laurentian 

 epoch §. 



" § 397. Whilst essentially belonging to the Nummuline 

 group, in virtue of the fine tubulation of the shelly layers 

 forming the ' proper wall ' of its chambers, Eozoon is related 

 to various types of recent Foraminifera in its other characters. 



• " This recognition was due, as Dr. Dawson has explicitly stated in 

 his original memoir ('Quarterly Journal of the Geological Society,' vol. xxi. 

 p. 54) to his acquaintance not merely with the author's [Dr. Carpenter's] 

 previous researches on the Minute Structure of the Foraminifera, but 

 with the special characters presented by Calcarina, as exhibited in thin 

 sections which had been transmitted to him by the author." 



t " See the Memoir of Profs. King and Rowney, in the Quart. Jouni. 

 Geol. Soc. vol. xxii. p. 185." 



\ "See Dr. Dawson's account of a specimen o^ Eozoon discovered in a 

 homogeneous limestone, in Quart. Journ. Geol. Soc. vol. xxiii. p. 257." 



§ " For a fuller account of the results of the Author's own study of 

 Eozoon, and of the basis on which the above reconstruction is founded, 

 see his Papers in Quart. Journ. Geol. Soc. vol. xxi. p. 59, and vol. xxii. 

 p. 219, and in the 'Intellectual Observer,' vol. vii. (18G5), p. 278." 



18* 



