112 



m, r, the oral ring. 



n, secretory apparatus. 



p, oral spines. 



r, radial caeca. 



st, stomach. 



X^ab. VII. 



B r i s i n g a e n d e c a c n e m o s. 



Fir/. 1. A full grown specimen viewed from above, natural size. One of the arms 

 is completely developed; another is' broken off near the middle, and the point recently 

 regenerated; a 3 rd is just newly formed. 



Fig. 2. The disc of the same specimen, somewhat magnified, viewed from the side. 



Fig. 3. The same viewed from below. The folds of the stomach are strongly pro- 

 truded; so that the oral membrane is not visible. 



Fig. 4. The madreporic body, with a piece of the dorsal skin, strongly magnified, 

 viewed from above. 



Fig. 5. A piece of the disc of another specimen, viewed from below, to shew the 

 oral membrane and the arrangement of the spines. 



Fig. 6. 3 of the dorsal disc-spines, with basal plates belonging to them imbedded 

 in the skin. 



Fig. 7. The oral ring viewed from above, magnified. 



Fig. 8. A piece. of the same, somewhat more strongly magnified, viewed from the 

 exterior side. 



Fig. 9. The same viewed from below. The spines are removed, with exception of 

 the rudimentary oral spines proceding from the extremity of the interior contiguous adambu- 

 lacral plates. 



Fig. 10. The disc of a very young specimen, viewed from above. 



Fig. 11. The base of a dessicated arm, viewed from the left side, slightly magnified. 



Fig. 12. Calcareous bodies and small spines from the dorsal skin of the same, 

 strongly magnified. 



Fig. 13. Extremity of one of the transversal calcareous ribs, with a marginal spine. 



Fig. 14. One of the small spines situated on the calcareous ribs, strongly magnified. 



Fig. 1.5. Base of the skeleton of the arm, viewed from above. 



Fig. 16. The same viewed from below. 



Fig. 17. The extremity of an arm, viewed from the left side and strongly magni- 

 fied. The preparation is treated with a solution of potash; so that the interior skeleton is 

 distinctly seen through the skin. 



Fig. 18. The basal half of an arm of a full grown female, viewed from above, 

 natural size. The dorsal skin is cut open along the middle and turned back on the sides, 

 to expose the numerous ovaries attached along both sides. 



Fig. 19. An ovary consisting only of a single caecum, isolated. 



Fig. 20. Another ovary, with incipient dichotomic division. 



Fig. 21. Base of an arm of a full grown male, viewed from above. The dorsal skin 

 is, as in the preceding preparation, cut open along the middle; its left half is removed, 

 while the right is spread out to expose the cluster-shaped seminaries. 



Fig. 22. A seminary isolated and more strongly magnified. 



