4(30 



MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



largest polyp (fig'. 85) the first two cycles of mesenteries sire fully established, a pair of metacnemes 

 having appeared within each of the six primary exocceles. 



n 



i 



Fig. 8a. 

 Aatrangia solitaria.—'Fig. 8. Series of diagrammatic figures {a-g) illustrating the order of appearance of the mesenteries of the first and 

 second cycles of metacnemes. a. Four isocnemic pairs of the first cycle of metacnemes are present (II), while three of the protocnemes 

 are not vet united with the stomoda-um. 



n 



n 



Fig. 86. 

 Astrangia soliiaria. — Tin- protocnemes arc all complete, and the six pairs of first-cycle metacnemes have all appeared. 



Fig. 8c presents the first appearance of the third-cycle mesenteries or second-cycle metacnemes, 

 which are to be especially studied. A new pair of mesenteries has appeared within the exocoele 



