THE DEVBLOPMENT OF ASTERINA GIBBOSA. 271 



hydrocoele. Bury (1) may be said to have introduced modern 

 conceptions of Echinoderm development by his work on the 

 development of Autedon; there he distinguished between an- 

 terior ccelom and hydroccele, and showed that the stalk was the 

 praeoral lobe. Then he made a series of observations on Echino- 

 derm larvae (2), and showed that generally speaking the coelom 

 on each side becomes segmented into two vesicles, an anterior 

 and a posterior. He, however, regarded the hydrocoele as an 

 essentially unpaired structure, an outgrowth from the anterior 

 coelom, and was greatly distressed to find that it originated 

 from the posterior vesicle in Ophiurids, and that in Asterina 

 the stone-canal, which in other forms represented the original 

 neck of communication between anterior ccelom and hydrocoele, 

 was apparently an independent perforation. The last difficulty 

 has been answered by Ludwigj^ as to the former, the proof I 

 have brought that the hydrocoele is paired shows that there are 

 really three primary divisions of the ccelom on each side, viz. 

 the anterior coelom, single in Asterina, but primitively paired 

 in Asterias; the right or left hydrocoele, and the posterior 

 coelom (right or left as the case may be) ; the apparent forma- 

 tion therefore of the hydrocoele from the anterior or posterior 

 vesicle is a mere question as to whether the septum between 

 the posterior coelom and the hydrocoele or the septum between 

 the hydrocoele and the anterior ccelom is formed first. 



In speaking of the Bipinnaria, Bury says that in a future 

 paper he intends to prove that the anterior coelom becomes the 

 axial sinus, but up till now he has published nothing further 

 on the subject.^ He made a few observations on Asterina 



' Bury had not seen the stage of development when the stone-canal is an 

 open groove. 



' Since the preliminary account (15) of the present paper was published, a 

 paper on the " Organogeny of Stellerids," by M. Achille Eusso, has appeared 

 in the 'Atti della Accadema reale di Napoli' for 1894. In this work (to 

 which I only obtained access some considerable time after the present paper 

 was finished) M. Russo gives a description of the ontogeny and anatomy of 

 the ovoid gland and axial sinus in Asterina gibbosa and an Ophiurid. He 

 combats mj statements about the origin of these structures in Amphiura 

 squamata. The origin of the axial sinus in Asterina has been correctly de- 

 scribed ; it is about the only thing that is correctly described in the paper. 



