NOTES ON THE OPHIURANS, OR THE SAND AND BRITTLE STARS. 353 
before the other. These have often granulations or spinules on 
their edges, and may be short or long. (Fig. 10 g, 2, 6.) A 
needle placed in one goes into the body, and if pushed on, will 
come out at the top through one of the ten large plates which 
are placed there close to the upper edge of the arm and on one 
side. These are the radial shields. (Fig. la.) If the needle 
is pushed inwards towards the mouth it will be stopped beneath 
the mouth shield on the under surface by the jaws as they pass 
inwards and sidewards from the arms : and if the instrument 
is pushed in the opposite direction it will be stopped by the 
inside of the edge of the disc. In fact, there is a space which is 
thus situated outside the stomach and jaw apparatus and beneath 
the shields, and it may be subdivided into ten, two in each 
interbrachial space, or there may be a greater or less general 
cavity extending from one arm space to another over the arm, 
forming a marsupium or pouch. In the spring time, the 
spaces are crammed and the disc is swollen with ova, red in 
colour, and there may be masses of white, which . are sperma- 
tozoa. They are in and amongst much connective tissue form- 
ing a set of bags. Water passes readily through the generative 
slits into the chambers, and at the proper time the ova burst 
forth to pursue a very remarkable metamorphosis. Years since, 
living and perfect tiny Ophiuroids were found in the pouch of 
the parent, and there is no doubt that then the ova are hatched 
within, and that the metamorphosis is skipped. 
DESCRIPTION OF PLATE VII. 
Fig. 1. The upper surface of a Sand Star, Ophioglypha Sarsii. a = A radial 
shield. 
Fig. 2. The under surface of the same Ophiuran. b = a mouth shield. 
Generative slits by the side of the arms. 
Fig. 3. The side of the arm showing (u) upper arm plates, and ( m ) side 
arm plates, carrying spines and minute tentacle scales. 
Fig. 4. View from below (in the proper position of the animal) of a jaw- 
angle in a species of Brittle Star, Ophiothrix. d = a jaw ; 
c = a side mouth shield ; 6 = mouth shield; tp = tooth papillae 
and at their end some teeth. The oval with the tooth papillae 
is aslant, and on a higher level in the natural position than the 
jaws d. A tentacle ( q ), the lowest of the angle, is seen on each 
side close to the side arm plates. 
Fig. 5. View from above of ends of teeth and jaws; the curved line 
marks the attachment of the membrane of the stomach, and 
external to it would be the position of the nerve cord, e = teeth ; 
ep = tooth or jaw plate ; d — jaws ; s = stomach line. The dotted 
lines note the line between the jaws. 
NEW SERIES, VOL. II. — NO. VIII. A A 
