STUDIES IN THE EMBRYOLOGY OF EOHINODERMS. 449 
Fig. 15. — Diagrammatic view of the left side of a large Bipinnaria, the 
larval arms and most of the prseoral lobe being cut away. Outline drawn with 
camera lucida. X 20. 
Fig. 16. — The same, from the right side. X 100. 
Eig. 17. — Larva of Asterina gibbosa on the seventh day of develop- 
ment, seen from the dorsal side. X 100. 
Fig. 18. — Part of the left side of an Ophiurid Pluteus, seen from the 
dorsal side, showing the origin of the hydroccel. X 510. 
Eig. 19. — Transverse section of an older Ophiurid Pluteus, passing 
through the posterior part of the oesophagus, x 540. 
Fig. 20. — Transverse section of a Pluteus of Echinus microtubercu- 
latus, showing the relation of the pedicellarise to the right body-cavity. 
X 180. 
Fig. 21. — The same part of another abnormal Auricularia, dorsal view. 
X 180. 
Fig. 22. — Part of an abnormal Auricularia, lateral view. X 180. 
Fig. 23. — Dorsal view of the same part of a normal Auricularia. Treatment 
with chloral-hydrate has caused retraction of the pseudopodia of the meso- 
derm cells. X 180. 
Fig. 24. — Lateral view of the same. The mesoderm cells are omitted. 
X 180. 
Fig. 25. — Part of a transverse section through an Auricularia, just entering 
into the “pupa” stage. X 300. 
Fig. 26. — Part of a transverse section of a larva of Cucumaria Plauci. 
X 300. 
Fig. 27. — Diagram of the hydrocoel of an old Auricularia, seen from the 
dorsal side. 
Fig. 28. — Diagram of the closure of the water-vascular ring in different 
groups of Echinoderms, dorsal (aboral) view. 
