496 TEANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. . 



Plate III. 



Fig. 20. Ventral view of a full-grown ophiopluteus 

 mancns. 



Fig. 21. Young specimen of the same. The coelomic 

 vesicles in optical section. 



Fig. 22. Ventral view of slightly older ophiopluteus. 



Fig. 23. Ventral view of a still older ophiopluteus. 



Fig. 24. Ventral view of a still older ophiopluteus in 

 an early stage of metamorphosis. 



Fig. 25. Ventral view of an ophiopluteus in which meta- 

 morphosis is just beginning. 



Plate IV. 



Fig. 26. Ventral view of a metamorphosing ophiopluteus 

 mancus. Only three lobes of the hydrocoel 

 can be discerned in this specimen. 



Fig. 27. Ventral view of a slightly older specimen, with 

 the hydrocoel as in fig. 26. For ad. in this 

 figure read 7n.pl. 



Fig. 28. Ventral view of a metamorphosing ophio- 

 pluteus mancus. 



Fig. 29. Dorsal view of an ophiopluteus mancus in 

 which metamorphosis is well advanced. 



Fig. 30. Dorsal view of an ophiopluteus mancus in which 

 metamorphosis is nearly complete. 



Fig. 31. Dorsal view of a post-larva, freed from the 

 pluteus, but still pelagic. 



Plate V. 

 Fig. 32. Ventral view of a full-grown ophiopluteus of 



Ophiothrix fragilis. 

 Fig. 32a. Posterior portion of the skeleton of the same. 

 Fig. 33. Ventral view of a young ophiopluteus of 



Ophiothrix fragilis. 



Fig. 34. Ventral view of a slightly older ophiopluteus of 



Ophiothrix fragilis. 

 Fig. 35. Dorsal view of an ophiopluteus of Ophiothrix 



fragilis. (Compare with fig. 29). 

 Fig. 36. Post-larval but still pelagic Ophiothrix 



fragilis. From an unstained preparation. 



