510 



MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



Fig. 16/ represents the mesenterial condition obtained from a transverse section through the 

 lower part of the stonioda'uiu of another decalcified polyp. The six protocnemic pairs are now 



n 



r 



Fig. 15/. 

 /"ario/rai/iim.— Young polyp in which all the pairs ot protocnemes (I) are united with the stomodajum, and the six pairs of first-cycle 



metaenemes (II) are developed. 



all complete, and six alternating pairs of metaenemes are fully established as a second cycle. 

 The next figure, from a somewhat larger polyp, shows the commencement of the third cycle of 



Fai'ia /rapion.— Polyp with six pairs of second-cycle metaenemes (III). The succession is from the dorsal to the ventral aspect. 



mesenteries (fig. 15f/); its development also is proceeding by isocnemic pairs in a dorso-ventral 

 or antero-posterior order. 



