THE BEGINNING OF LIFE ON THE EARTH. 39 



with each other by hollow tubes from which proceed canals 

 perforating the plates (Fig. 25). This curious structure is 

 confined to the Siluro-Cambrian, and is so dissimilar from 

 modern forms that its affinities have been subject to grave 

 doubts. 



We thus have presented to us the remarkable fact that in 

 the Palaeozoic age we have no precise representative of Eozoon, 

 but instead three divergent types, differing from it and from 



Fig. 26.— Section of Lofttisia Persica. An Eocene Foraminifer allied to Stromatopora. 

 Magnified five diameters,— After Carpenter and Brady. 



each other, all apparently specialised to particular uses, all 

 tempon.jy in their duration ; while in later times nature seems 

 to have returned nearer to the type of Eozoon, though on a 

 smalle*- scale, and separating some characters conjoined in it. 

 Some portion of this curious result may be due to our ignorance ; 

 and it would be interesting to know, what we may know some 

 day, how this type of life was represented in the long interval 

 between the Huronian { nd the Upper Cambrian, when perhaps 



