NOTES ON L.M.B.C. ASTEROIDEA. . 235 
ossicles each one gives off on either side a great number 
of lateral branches which open into the cavities of the 
tube-feet. The fluid which occurs in these vessels contains 
amoeboid corpuscles. Of the tube-feet there are two 
usually straight, but in Asterias sharply zig-zaged rows, 
lodged in the ambulacral grooves. Hach tube-foot is 
provided with a vesicular ampulla lodged within the cavity 
of the ray. Communication between the two is established 
by a canal which passes upwards from the base of the 
foot through a corresponding pore formed by grooves in 
the two adjacent ambulacral ossicles. In many genera the 
tube-feet terminate in sucker-discs, but those of Astropecten 
and Luedia are conical at their free ends. 
The nervous system consists of a plexus of nerve fibrils 
and ganglion cells which underlies the ectoderm. At the 
bottom of the ambulacral grooves the fibres are much 
more numerous, and run parallel with the axis of the ray. 
In transverse sections they appear as minute dots between 
the filiform inner ends of the ectoderm cells, which are 
here enormously elongated, and form a ridge-lke thicken- 
ing, the ambulacral nerve. Hach radial nerve joins its 
fellows on either side to form the circum-oral nerve-ring 
(Pl. XXX VIII, figs. 1 and 8, nv). The generative organs 
consist of sacculated glands, of which there is a pair in 
each ray. Hach gland is attached to the lateral wall of 
the ray, near its base, and opens by a single pore, or 
rarely by a number of pores. In the genus Brisenga each 
ray contains a number of distinct glands, arranged serially 
along each side of the ray, and opening by separate pores. 
Having thus briefly surveyed the general organisation 
of starfishes, I now proceed to a discussion of the minute 
anatomy of the two systems mentioned at the outset. 
Careful examination of a large number of sections of the 
madreporite of Asterias, Cribrella, Astropecten and Aste- 
