THE DEVELOPMENT, OF ASTERINA GIBBOSA. 389 
hydrocele. Bury (1) may be said to have introduced modern 
conceptions of Echinoderm development by his work on the 
development of Antedon; there he distinguished between an- 
terior celom and hydroccele, and showed that the stalk was the 
preoral lobe. Then he made a series of observations on Echino- 
derm larve (2), and showed that generally speaking the celom 
on each side becomes segmented into two vesicles, an anterior 
and a posterior. He, however, regarded the hydrocele as an 
essentially unpaired structure, an outgrowth from the anterior 
ceelom, 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 celom and hydrocele, 
was apparently an independent perforation. The Jast difficulty 
has been answered by Ludwig;! as to the former, the proof I 
have brought that the hydrocele is paired shows that there are 
really three primary divisions of the coelom on each side, viz. 
the anterior celom, single in Asterina, but primitively paired 
in Asterias; the right or left hydrocele, and the posterior 
ccelom (right or left as the case may be); the apparent forma- 
tion therefore of the hydroccele from the anterior or posterior 
vesicle is a mere question as to whether the septum between 
the posterior coelom and the hydrocele or the septum between 
the hydrocele 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 
1 Bury had not seen the stage of development when the stone-canal is an 
open groove. 
2 Since the preliminary account (15) of the present paper was published, a 
paper on the “‘ Organogeny of Stellerids,” by M. Achille Russo, 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 my 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, 
