POSTLARVAL DEVELOPMENT. 



8l 



A dorso-ventral sequence in the development of the six pairs of second- 

 cycle mesenteries, as compared with their simultaneous appearance, has long 

 been known in actinians ; in fact, from the time of the Dixons' account of 



Ila 



Ila 



Ilia 



Ilia 



n 



Illb 



II 



IIIc 



FIG. 8 (<,/,/,*), continued. Scries of diagrams illustrating the order of development of the first three cycles of mesenteries. 

 e andy represent the second and third stages for second cycle, and/ and k are two early stages of third cycle. 



the relative sizes of the pairs in certain late larvae of Bunodes. Apparently, 

 however, the present is the first occasion on which the actual appearance has 

 been followed stage by stage in the living polyp. 



The developmental stage now reached is one which frequently recurs 

 in zoantharian studies. Of the protocnemes, the eight Edwardsian members 



