32 



THE CHAIN OF LIFE. 



produced the calcareous skeleton of Eozoon was a ttiember of 

 that lowest grade of Protozoa known as Foraminifera; and which, 

 after living through the whole of geological time, still abound 

 in the sea. The main differences are, that Eozoon presents 

 a 'somewhat generalised structure, intermediate between two 

 modern types, and that it attained to a gigantic size compared 

 with most of these organisms in later periods. How near it 

 approaches in structure to some modern forms may be seen by 

 comparison of the recent species represented in Fig. 19 



in 



Fic;. 19. — Magnified portion of shell of Calcarina — ^After Carpenter. 

 a. Cells. /', Original cell-wall with tiibull. c, Supplementary skelatcn with canal-; 



which the parts corresponding to the chambers, laminae, tubuli, 

 and canals of Eozoon can be readily distinguished. 



The modern animals of this group are wholly composed of 

 soft gelatinous protoplasm or sarcode, the outer layer of which 

 is usually somewhat denser than the inner portion ; but both are 

 structureless, except that the inner layer may present a more 



