FORAMINIFERA. 63 



formations into which the stratified series is divided, from the 

 Laurentian period to the present day. In one of the limestones 

 of the vast Laurentian series of Canada occurs a singular body 

 which has been described as a gigantic Foraminifer, under the 

 name of Eozoon Canadense (fig. 10). Some observers doubt 

 the true organic nature of Eozob'n, but the weight of authority 

 is decidedly in favour of the belief that the above is its real 

 character. If this be the case, Eozoon is not only the oldest of 

 the Foraminifera, but is the earliest fossil of any kind as yet 

 discovered. Eozoon consists of a chambered calcareous skele- 



a -\?'? ...... '; .." 



A 



Fig. io. Diagram of a portion of Eozoon (after Carpenter). A, B, C, Three tiers of 

 chambers communicating with one another by constricted apertures ; a a The true shell- 

 wall, perforated by numerous pseudopodial foramina; b b Intermediate skeleton ; c Pas- 

 sage of communication (stolon-passage) from tier to tier ; d Ramifying tubes in the inter- 

 mediate skeleton. 



ton infiltrated by certain silicates in solution. These silicates 

 are chiefly white pyroxene, serpentine, and Loganite, and they 

 are now found occupying all the spaces in the fossil which were 

 formerly filled with the sarcode of the animal. When, there- 

 fore, a specimen of Eozoon is treated with acid, the calcareous 

 matter is dissolved out, and what we have left consists of a 

 cast in the above silicates of the chambers formerly occupied 

 by the sarcode of the animal, together with the various passages 

 by which these chambers are connected, and the tubes by 

 which the pseudopodia were conducted to the exterior. That 

 such a replacement of an animal body by silicated minerals 

 is not an impossibility is shown by the occurrence of casts of 

 living Foraminifera (such as Amphistegina) in which the sarcode 

 is replaced by a green silicate (probably glauconite), which 

 forms an accurate cast of the interior of the shell. Eozoon 

 consists essentially of a series of chambers placed in tiers 

 (fig. io, A, B, C) which are arranged one above the other. 



