WORLD-BUILDERS. 7 



said the shells fell to the bottom of the ocean in its 

 shallower parts, because at the greater depths of the 

 ocean the sea water through which they gradually sink 

 to the distant ocean floor dissolves the delicate shells 

 and gets back the lime of which it was robbed by the 

 living animals before their empty houses can collect 

 at the bottom ; so that soundings at great sea depths 

 show no trace of foraminifera, as these tiny house- 

 builders are called. 



Latticed infusoria. 



