260 



Plate XXVI. 



Fig 1. Ophiopluteus arcifer, species a. ^s/^. 



2. - - - b. ««/i- 



3. - _ _ c. "A. 



Plate XXVII. 



Fig. 1. Ophiopluteus formosus, species a. '^/j. 



2. — _ — b. Sliglitly restored. »7i. 



3. — similis. *^/i. 



Plate XXVIII. 



Fig. 1. Ophiopluteus serratus. «7i- 



2. — , beginning metamorpliosis. *"/x. 



Plate XXIX. 



Fig. 1. Ophiopluteus pusillus, species a. "Vi- 

 2. — _ _ b. "Vi- 



3_ — — -; in metamorpliosis. ^^^/i- 



The remnants of tlie vibratile band to be noticed. 



4. Ophiopluteus pusillus, species c. "Vi- 



5. — _ _ d. i»Vi- 



6. diegensis. "Vi- The small spots in the posterior part of the body 



are pigment cells. 



Plate XXX. 



Fig. 1. Ophiopluteus of Ophiocoma, species c. slightly restored. i»Vi- 



2. — formosus, species a. in metamorphosis. 'Vi- 



3. — monacanthas. °°/i- 



4. — — , in side view, somewhat distorted. *"/i. 



Plate XXXI. 



Fig. 1. Larva of Ophionereis squamulosa Koehler; 45 hours old. Drawn from life. Ventral 

 view, ^""/i- 



2. Same larva, same age. Dorsal view. The 6 primary plates and three of the terminal 

 plates have appeared; the oral skeleton has not yet appeared in this specimen, 

 c. b. ciliated band; hp. hydropore; pr. t. primary tentacle; tf. 2 second pair of 

 tubefeet. ^^U- 



3. Same larva, 2^/2 days old ; from the ventral side. The mouth opening has been formed. 

 Letters as in flg. 2; further stc. stone canal; b. t. buccal tentacles. ^^Vi- 



4. Same larva, 6 days old; the metamorphosis nearly completed, but the anterior end 

 of the larval body and traces of the ciliated bands (cb.) are still distinctly visible. 

 The first ventral plate (v.) and the first side plate with its spine have been formed. 

 The mouth shields have not yet appeared, t. terminal plate. "^Ii- 



5. Longitudinal, frontal, section of larva of Ophionereis squamulosa, 26 hours old; 

 e. c. enterocoel; h. hydrocoel; st. stomach, ^'"/i- 



6. Larva of same species, 26 hours old; drawn from a cleared up specimen. The hydro- 

 coel is in a more advanced stage than in Fig. 5, showing the five radial canals. The 

 enterocoel is indistinct, st. stomach, '■'"/i. 



7. Cleavage stage of Amphiura vivipara. '^''■"/i- 



8. Further advanced stage of the same; the nuclei have arranged themselves in a 

 layer along the surface so as to form the ectoderm, ""/j. 



9. Young embryo of Amphiura vivipara, showing the arms curved over the dorsal 

 side, in the skin of which the primary plates are observed, irregularly arranged, '"/i. 



Plate XXXII. 



All figures of Ophionotus hexactis (E. A. Smith). 

 Fig. 1 — 2. Young larva with a right hydrocoel. 1 from the ventral side, 2 in side view. ""/j. 



