105 



Fig. 11. The disc of another likewise ll-armed specimen seen from above, after 

 that the dorsal skin and all the interior organs situated in the cavity of the disc have been 

 removed, whereby the skeleton (the oral ring), with its tendinous lining membrane, is en- 

 tirely exposed: a, the madreporic body, with the sheath preceding downwards from the 

 same, in which the so-called ,,heart" is inclosed; 6, the oral membrane; c c, the fan-like 

 extended tendinous fibres issuing from the upper border of the oral ring and attaching the 

 peripheral part of the stomach; d d, glandulous corpuscules attached to the periphery of 

 the circular ambulacral vessel; e, the oral aperture. 



Fig. 12. A piece of the oral ring with the tendinous membrane that lines the same, 

 viewed from the interior sides a, the madreporic body; 6, the oral membrane; c, the tendi- 

 nous sheath in which the ,,heart" is inclosed; d d, the glandulous corpuscules attached in 

 the periphery of the circular ambulacral vessel; e, the stone canal. 



Fig. 13. Some of the granulous contents of the corpuscules (d), strongly magnified. 



Fig. 14. One of the glandulous corpuscules isolated. 



Tab. III. 







Fig. 1. Part of the disc from the side, magnified, shewing the articulating surfaces 

 for an arm and the adjacent parts: a, section of the radial nerve with the blood-sinus 

 above it; 6, section of the radial ambulacral vessel; c, ampullae for the exterior water-feet 

 of the disc ; d, section of one of the radial caeca. 



Fig. 2. Part of the disc viewed from below. The spines and the water-feet are for 

 the greater part removed, in order to show the arrangement of the nervous system: a a, the 

 radial nerves; b 6, the circular commissure of the nerves (see also Tab. VI, fig. 1). 



Fig. 3. Transverse section of the basal part of an arm of a full grown female specimen: 

 a, the water-feet; b, vertebra; c c, the ampullae for the water- feet, projecting into the cavity 

 of the arm; d d, section of the 2 branches of the radial caeca; e e, section of the ovaries; 

 f f, marginal spines. 



Fig. 4. The basal part of an arm of a full grown female viewed from above, a 

 little magnified. The dorsal skin is cut along the middle and extended on each side, to 

 expose the strongly ramified ovaries situated in the cavity of the arm. Along the middle, 

 the skeleton of the arm's appears; and on each side of it, we see the ampullae for the 

 water-feet arranged in pairs. 



Fig. 5. An ovary of more compact form, isolated and viewed from the interior side. 



Fig. 6. The same viewed from the exterior side: a, a piece of the skin of the 

 arm, with the exterior genital aperture (b) situated in the same. 



Fig. 7. A branch of an ovary, with (terminal) ramified cylindrical caeca. 



14 



