122 PROTOZOA. 



group of organisms regard Eozoon Canadense as an aberrant 

 IsTummuline Foraminifer, there are other observers who look 

 upon it as a purely mineral and inorganic structure. 1 If, 

 however, we accept the Foraminiferal nature of Eozoon as, 

 at any rate, highly probable, we are presented here with a 

 type of extraordinary interest, not only from its intrinsic 

 peculiarities, but also as the most ancient representative of 

 the group of Foraminifera, and, indeed, as the oldest fossil 

 which has yet been exhumed from the earth's crust. 



The structure known as Eozoon is found in various locali- 

 ties in the Lower Laurentian limestones of Canada, in the 

 form of isolated masses or spreading layers, which are com- 

 posed of thin alternating laminse, arranged more or less con- 

 centrically (fig. 25). The laminae of these masses are usually 



Fig. 25. Fragment of Eozoon, of the natural size, showing alternately laminse of loganite 

 and dolomite. (After Dawson.) 



of different colours and composition ; one series being white, 

 and composed of carbonate of lime whilst the laminae of 

 the second series, alternate with the preceding, are green in 

 colour, and are found by chemical analysis to consist of some 

 silicate, generally serpentine or the closely related " loganite," 

 or white pyroxene. In some instances, however, all the 

 laminse are calcareous, the concentric arrangement still re- 

 maining visible in consequence of the fact that the laminae 



1 Since the above was written, Professor Mobius has published an elaborate 

 treatise upon Eozoon, and has arrived at the conclusion that it is not truly 

 organic. It would not appear, however, so far as the author is able to judge, 

 that the arguments of Mobius are by any means decisive ; and it may safely 

 be concluded that the last word on Eozoon has yet to be spoken. 



