THE DEVELOPMENT OF ASTERINA GIBBOSA. 391 
a preoral sense-organ is present; this subsequently becomes 
incorporated with the ciliated ring, and if this organ is homo- 
logous with that of the Bipinnaria, we may conclude that the 
ciliated band of the Pluteus corresponds only to the posterior 
of the two bands of the Bipinnaria, since in the Bipinnaria 
the sense-organ is situated between preoral and post-oral 
ciliated bands, and this spot corresponds to a constriction in 
the original longitudinal ciliated ring, not to a position on its 
anterior edge. 
Our knowledge of Echinoderm histology is largely due to 
Hamann (8) and Cuénot (3 and 4). The latter, as we have 
seen above, was the first to suggest that the ovoid gland gave 
rise to the genital rachis. The first account of the development 
of ovoid gland and rachis is given in my paper on Amphiura 
squamata (14), and I have there collected the fragmentary 
notices on this subject, which had till then appeared. 
[I regret that when I sent in this paper for publication I did 
not mention the well-known paper of Metschnikoff (“ Studien 
tiber die Entwickelung der Echinodermen und Nemertinen,” 
‘Mémoires de l’ Académie Impériale de St. Pétersbourg,’ tome 
xiv, No. 8), in which he describes a right hydrocele in 
Amphiuriasquamata. He there says that the right coelomic 
vesicle becomes divided into anterior and posterior portions 
just like the left ; the anterior portion sometimes atrophies but 
sometimes develops into a regular five-lobed hydrocele. It 
has been the fashion to ignore this work, since it was not 
accomplished by modern methods; but after my experience 
with Asterina I feel morally certain that Metschnikoff was 
right, though of course he did not distinguish between 
hydroceeles and anterior celom. Bury (2) seems to have missed 
the importance of this observation.—Dec., 1895.] 
General Considerations. 
On reviewing the developmental history recorded in this 
paper, two main questions present themselves: first, what 
light does it throw on the affinities of the Asterids with other 
Echinoderms? and second, does it suggest any direction in 
