90 THE PRIMARY PERIODS. 



points, and yet they are perforated by numerous pores 

 (foramina, hence the name of the order), through which 

 the creature procures its food and holds intercourse with 

 the outer world of waters. Individually minute, they live 

 in colonies, and only become conspicuous by their aggrega- 

 tions, which in the instance of the eozoon vary from a few 

 inches to a foot or two in diameter. The white calcareous 

 mud which covers so much of the Atlantic sea-bed is a 

 similar foraminiferal accumulation; so is the nummulitic 

 limestone which stretches eastward in a great zone through 

 Europe and Asia ; so also is a large proportion of the chalk- 

 hills of England ; and so backward in time through other 

 limestones, till we reach the oldest and earliest Laurentian 

 marble. With a little manipulation, the organisms constitut- 

 ing the existing sea-muds or the chalk are readily revealed ; 

 but the old eozoon has to be polished, cut into microscopic 

 slices, and treated with acids before the peculiarities of its 

 structure can be rendered intelligible. So great is the 

 change produced by the mineralisation of ages.* Strange 

 that the minutest of organisms should be capable of piling 

 up such stupendous rock-masses ; strange and suggestive 



* We are aware some geologists have called in question the organic 

 nature of this Canadian eozoon regarding it merely as a peculiar mineral 

 structure mimetic of the organic, examples of such simulative structures 

 being well known in other formations. The majority of competent ob- 

 servers, however, maintain its organic nature ; and from a conversation 

 we had, in the autumn of 1865, with Principal Dawson of Montreal, who 

 has examined the rocks in situ, with their unobliterated lines of deposi- 

 tion and layers of organic growth (brought out more clearly by weather- 

 ing), we share the conviction that the Eozoon Canadense, whatever be 

 its zoological affinities, is of animal and not of mineral aggregation. To 

 the practised eye external appearances are often conclusive of organic 

 structure, and these, in the present case, had been observed and accepted 

 before the microscope was called into court to complete the evidence. 

 Those interested in this matter may refer to the papers by Dr Carpenter, 

 Professor King, and others, in the Journals of the Geological Society for 

 1865 and 1866. 



