MORPHOLOGY OF THE MADREPORARIA. 85 



nent d'etre formees. Les cycles naissent successivement et 

 jamais un cycle ne commence a se former avant que le precedent 

 soit complete." Similarly J. Stanley Gardiner (1902, p. 133) in 

 his account of the anatomy of Flabcllum nibrum says (italics 

 added) : " As the growth of any corallite proceeds, more and 

 more septa up to six cycles appear. The fanner exoccclic order 

 of septa becomes entoccelic by the development of new pairs of mesen- 

 teries. The increase of mesenteries takes place pari passu with 

 the formation of new septa." 



Unfortunately, the relationships involved in the above asser- 

 tions have not been actually followed, though from the known 

 conditions no other arrangement at first sight seems possible ; and 

 it was principally with a view to determine the truth or otherwise 

 of the assumption that the present investigation was undertaken. 



FIG. 5. First appearance of the permanent second cycle of entosepta situated 

 within the entocceles of the second cycle of mesenteries and the bifurcations of the 

 dorsal and middle exosepta. 



Shortly after the stage represented in Fig. 4 was reached inde- 

 pendent calcareous growths began to arise peripherally, in posi- 

 tions corresponding with the entocoeles of the second cycle 

 mesenteries ; those within the dorsal entocceles were larger than 

 the ones within the middle entocceles, while for a long period 

 there was no corresponding formation within the ventral entocoele 

 (Fig. 5). At first the structures were quite free and resembled 



