22 



EOZOON. 



top-shaped form, sometimes with a depression on the 

 upper surface, giving it the appearance of the ordinary 

 cup-shaped Mediterranean sponges." 



A hand specimen of Eozoon shows it to consist of 

 alternating layers of a green mineral, serpentine, and a 

 white mineral, calcite. In thin sections viewed under the 

 microscope, the serpentine is seen to have at times a 

 fairly regular and more or less beaded form. This layer 

 is considered by Dawson and Carpenter to fill the space 

 which was originally occupied by the soft parts of the 

 animal (fig. 4, b), the serpentine having been introduced 

 subsequently by infiltration, and thus forming a cast of 

 the body chambers. On each side of the serpentine and 

 between it and the layer of calcite, there may be seen in 

 good specimens a thin lamina (a), said to be calcareous 

 and perforated by numerous tubules ; this lamina is com- 



FIG. 4. Diagram to explain the organic theory of Eozoon. a, body- wall ; 

 b, body chamber ; c, supplemental skeleton ; d, canals in the sup- 

 plemental skeleton ; e, stolon-passages. 



pared with the body-wall of the Foraminifera such as 

 GloUgerina, the tubules being the perforations for the 

 passage of the pseudopodia. External to the body-wall 

 is the thick layer of calcite (c), having the characteristic 

 cleavage of that mineral; this is traversed by numerous 



