THE DEVELOPMENT OF ASTERINA GIBBOSA. 379 
have greatly developed, and have grown in between the radii on 
to the oral surface, forcing the original oral plates to the extreme 
centre of the disc; and so the stone-canal has been swung round 
and the genital rachis pulled out of shape. Nowin Asterina 
gibbosa there is a trace of this process; the rachis does 
not, as Hamann (7) has described in Asterias, lie in one plane, 
but pursues an undulating course, being much more aboral in 
the radii than the interradii. I am inclined to look upon this 
as the primitive condition from which the Asterid and Ophiurid 
arrangements have been derived. I may as well mention here 
some other facts which indicate the primitive nature of Asterina. 
Chief among them is, that in the family of which it is a member 
we meet with the most rudimentary form of those characteristic 
Asterid organs the pedicellariz. We have in Asterina the 
aboral surface covered with small spines, arranged in twos and 
threes, and acting on irritation like pedicellariz. It is true 
that some Asterids have no pedicellariz, but here the evidence 
from allied genera (cf. Luidia and Astropecten) suggests that 
they have been lost; Asterina, however, shows us pedicellariz 
in statu nascendi. The simple biserial tube-feet also con- 
stitute a primitive character. 
Fig. 118 represents ovoid gland and stone-canal in the 
latest stage examined by me. The gland is attached by an 
exceedingly narrow pedicle to the wall of the axial sinus. 
Its surface is thrown into deep folds, and the peritoneal 
lining of the axial sinus, which forms its outer covering, is 
modified, consisting of cylindrical cells with projecting rounded 
ends. The interior of the gland is filled with a mass of primitive 
germ cells supported by fibres, doubtless of mesenchymatous 
origin. I was unable to find any trace of a tube lined by 
primitive germ cells, such as was discovered by Hamann in 
the young Asterias. 
What, we may finally ask, is the function of this strange 
organ? Cuénot, as usual, maintains that it 1s a lymphatic 
organ. This I am disposed to doubt very strongly; the 
cells which it contains are of quite a different nature from 
the amcebocytes of the oral blood-ring, and the evidence that 
