130 MINUTE MARVELS OF NATURE 



limestone strata. With the true corals also, they 

 occur in particular abundance, and often form a 



Fig. 84. A stony sea-weed and its companion 

 stone-masons. Actual size shown to the left 



sort of mortar which holds the reef-building 

 corals together. This community of employment 

 between animals and plants is illustrated in 



