9 6 



SIDERASTREA RADIANS. 



Three important results in the development of the Madreporarian 

 skeleton are thus gained: (i) The primary exosepta do not continue their 



FIG. xo (-/"). Series of diagrammatic figures illustrating the relationships of the mesenteries and septa in the establishment 

 of the first two cycles of mesenteries and three cycles of septa. 



growth peripherally in a radial manner, and constitute entosepta by becoming 

 included within the entocoeleof the new second-cycle mesenteries. (2) The 



