SEA-FAN MAKERS. 



193 



spicules (fig. 37) met with seem to occupy certain 

 definite portions of the ectodermic layer, yet there is 

 an evident gradation between them, from the smooth, 



FIG. 37. SPICULES OF ORGAN CORAL. 



fusiform spicule to the most irregularly warty forms, 

 which leads naturally to the inference that all these 

 forms are but different stages of growth, by the 

 aggregation of new calcareous material, until the 



O 



