72 



THE DAWN OF LIFE. 



and other scHistose rocks interstratified with the 

 Laurentian limestone. In this way, in short,, Eozoon 

 would perform a function combining that which corals 

 and Foraminifera perform in the modern seas ; forming 

 both reef limestones and extensive chalky beds, and 

 probably living both in the shallow and the deeper 

 parts of the ocean. If in connection with this we con- 

 sider the rapidity with which the soft, simple, and 

 almost structureless sarcode of these Protozoa can be 

 built up, and the probability that they were more 

 abundantly supplied with food, both for nourishing their 

 soft parts and skeletons, than any similar creatures in 

 later times, we can readily understand the great 

 volume and extent of the Laurentian limestones which 

 they aided in producing. I say aided in producing, 

 because I would not desire to commit myself to the 

 doctrine that the Laurentian limestones are wholly of 

 this origin. There may have been other animal lime- 

 stone-builders than Eozoon, and there may have been 

 limestones formed by plants like the modern Nullipores 

 or by merely mineral deposition. 



Its relations to modern animals of its t3^pe have been 

 very clearly defined by Dr. Carpenter. In the structure 

 of its proper wall and its fine parallel perforations, it 

 resembles the Nummulites and their allies; and the 

 organism may therefore be regarded as an aberrant 

 member of the Nummuline group, which affords some 

 of the largest and most widely distributed of the fossil 

 Foraminifera. This resemblance may be seen in fig. 

 19. To the Nummulites it also conforms in its 



