ciliation of asterids. v 



6. Relation of Larval to Adult Oiliatioist. 



"While it is true that the larval ciliation passes into that of 

 the adult, the changes in shape and structure which take place 

 at metamorphosis are so profound that in the end only a few 

 details of correspondence between the two systems can be made 

 out. Taking Asterias rubens as the type, we note that the 

 oralward ciliation of the circumoral field (food-gathering area, 4, 

 p. 240) in the larva is probably related to the oralward ciliation 

 of the ambulacral grooves in starfish generally and in Crinoids. 

 In further correspondence, we find that the whole or greater part 

 of the buccal membrane in Astropecten,, Porania, and Solaster is 

 ciliated towards the mouth. Perhaps the outwardly lashing cilia 

 of the peristomal band (4, p. 239) on the lower lip of the larva 

 may have supplied the basis of the similarly acting cilia at the 

 actino-stomial margin of Porania. 



Text-fis-ure 2. 



OCT. 



Illustrating the circular movement of the coclomic" fluid in the late larva 

 and in the perivisceral cavity of the adult. 



ac.h, ac.r., left and right anterior cceloms ; mc.l., mc.r., left and right middle cceloms ; 

 dh., vh., dorsal and ventral horns of the left posterior ccelom ; hy., hy.', hydro- 

 ccele, and right hydrocoolic region ; Ipc. (hyjp.), left posterior or hypogastric 

 ccelom ; rpc. (epg.), right posterior or epigastric ccelom. 



Within the perivisceral cavity of the adult, the slight circular 

 dextral movement of the contained fluid appears to be represented 

 in the late larva by a circuit which includes the left posterior 



