104 



Dr. J. E. Duerden on the 



on the right side (/F, E). New mesenteries thus occur at 

 the two axial extremities of the polyp, within both the dorsal 

 and the ventral entocoeles, and each stomodfeum has asso- 

 ciated with it a dorsal and a ventral pair of directives, as in 

 ordinary adult polyps. 



Fig. 6 represents the final stage. Eight mesenteries now 

 stretch from each stomodjeum to the body-wall, and the two 

 tubes are wholly disconnected. The two additional mesen- 

 teries [F, F) are disposed within the entocoele of the dorsal 

 pair of mesenteries (£", E) shown to be added in the previous 

 figure, and the retractor muscle is arranged on the faces turned 



A B C D C BA 



KiG. 0. 



Transverse section tlirough a third polyp in which the two stomociaeal 

 tubes are altogether distinct from one another. Four pairs of mesen-' 

 teries, A-JD, have been added withiu the ventral entoccele, and two 

 pairs, JE, F, within the dorsal entocoele. 



towards each other, so that each mesentery will form an 

 isocnemic pair with the corresponding incomplete mesentery 

 {D) on the ventral aspect, a pair comparable with the mesen- 

 teries 7/ and V of the simple polyp. The mesenterial system 

 associated with each stomodgeum is now constituted exactly 

 as if each represented a distinct polyp (cp. fig. 1). 



The three sections from separate polyps clearly demon- 

 strate that in Madrepora new mesenteries beyond the proto- 

 cnemes are added in bilateral pairs within the primary ento- 

 coele of the dorsal directives and also of the ventral directives. 



