i,lo MINUTE MARVELS OF NATURE 



limestone strata. With the true corals also, they 

 occur in particular al)undance, and often form a 



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

 stone-masons. Actual size shown to tVie left 



sort ot mortar which holds the reef-building 

 corals together. This community of employment 

 between animals and plants is illustrated in 



