GOTO. — EMBRYOLOGY OF STARFISH. 335 



canal alone is present. I believe that they are also phylogenetically 

 distinct, the stone-canal being a later formation. In comparing the 

 Echinoderms with such a group as the Enteropueusta it is, as it 

 seems to me, the pore-canal alone that is primarily to be taken into 

 consideration. 



(6) The opening of the pore-canal and the stone-canal into the body 

 cavity persists throughout life. This is true not only of Asterinn gib- 

 bosa and Asterias pallida, but also of Asterias tenera, Solaster endeca, 

 and Gribrella sanguinolenta, and inferentially of all starfishes. The 

 opening of the stone-canal is always on the right side of the sagittal 

 plane. 



(7) In agreement with MacBride, I find that the " dorsal organ " of 

 Bury, the " Centralblutgeflecht " of Ludwig, forms the perioesophageal 

 portion of the body cavity of the adult. It arises in the form of a tube 

 from the left posterior enterocoel just behind the pore-canal. In a 

 young Brachiolaria it encircles about one fourth of the whole circum- 

 ference of the cardiac portion of the stomach, and it forms a complete 

 ring in a young star that has just finished its metamorphosis. The 

 septum that divides- it from the left posterior enterocoel is subsequently 

 completely absorbed except in one place, viz. the madreporic inter- 

 radius, where it appears to persist throughout the life of the animal. 

 The term "oral coelom," used by MacBride, seems to me unfortunate, 

 as that term has been applied to another and entirely different cavity 

 (left coelom) in Crinoids. I therefore prefer to call the structure in 

 question " perioesophageal enterocoel." 



(8) The perihsemal spaces (the inner ring excepted) as well as the 

 peribranchial spaces are, according to my observation, of true schizoccel 

 origin. 



Cambridge, April 8, 1896. 



