4i)2 



.ME.MOIKS OF THE NATIONAL ACADEMY OF SCIENCES. 



It must 1)6 bonic in iiiiiid tliiit the protocnemes lire pnutieully established at the time the 

 larva settles, and that no skeletal furinatioii takes place before the sedeiitarj- stage is assumed. 

 During- the sul)se(iueiit growth of the coral, the new septa (metasepta) are found to arise in a 

 dorso-veiitral succession, approximately 7^^^/ 7>r/.s-.s» with the pairs of mesenteries, and it may he 

 conceived that if the larva» settled witii only a few jiairs of mesenteries developed then the primary 

 septa would show a corresponding succession in their appearance. 



In most adult polyps of ]'<ir!tvf< and Mmlrepont the protoseptal stage is retained, six ento- 

 cfelic members and six exoctelic forming a larger and a smaller cycle. Very often some of the 

 twelve septa are wanting. :in(l usually one or both of t!ie directive septa are much larger than 



Fig. 12. 

 Skkrastr.ra rndians. — .Series ilhistratinf; llic dcvelopmem <A the protosepta in liir\ iil polyi)s. Tlu' ouht while ring represents the epitheca. 

 a. Six equal entosepta are present, developed simultaneously, fc, Six e<iuaKsmalleri'xosepta now oeeur, also developed simultaueonsly, 

 and alternating with the six primary entosepta. c. Successive appearance of the exosepta from the dorsal to the ventral aspect of the 

 polyp, observed in ti few eases, 



the latei'al, thus exhibiting a liilatcral syiiimetry. corresponding with that of the mesenteries and 

 tentacles. 



The young bud of Jladrejwni, repvesenU'd in section on I'l. ill. pro\es that in asexual 

 growth all the pi-otocnemes may make their appearance before se])tid ilevelopnient commences, so 

 that it seems not improl)al)le that the protosepta may arise simultaneously in bud as well as in 

 larval polyps. 



It is manifest from the examination of l)uds of other genera that tlie septa occur in accordance 

 with the number of the mesenteries at any particular stage, or at any rate their downward 

 extension is in conformity with the mesenteries present. It is found thtit as the mesenteries 



