260 



Plate XXVI. 



Fig. I. Ophiopliitfus arci/cr, .speck's a. '"/p 



- 2. — — — b. *»/,. 



- 3. — _ _ c. »»/,. 



Plate XXVII. 



Fig. 1. Ophiopliilctis /iirniDsits, species a. "'/,. 



- 2. — - b. Slii>lilly roslored. »»/,. 

 3. — similis. "/,. 



Plate XXVIII. 



Fig. 1. Opiiioptiilnis srrniliis. ""/,. 



2. — — , beginning metamorphosis. '"/,. 



Plate XXIX. 



Fig. 1. Ophidphiliiis piisilliis. species a. "^/,. 



- 2. - b. "Vi. 



3. -; in metaniorpliosis. "^/j. 

 Tlu' rciniianis ol the vibralile band Lo be noticed. 



4. Ophiopliilcits ptisillua, species c. '"^Z,. 



- 3. — - — d. >»/,. 



6. — diegensis. '"^/j. Tlie small spots in lia' posterior [tail of tlie body 



are pijiniciit cells. 



Plate XXX. 

 1^'ig. 1. OpIiKipliilcus ot Ophidfdinu, species c. slightly restored, '"''/i- 



2. — /ormosus, species a. in nielainoriiliosis. '■'Vj. 



3. — nioiiacanthus. ^°/i- 



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



Plate XXXI. 



Fig. 1. Larva of Ophioncreis sqiiamulosa Koehler; 45 hours old. Drawn from life, \entral 

 view. 120/^. 



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

 plates have a])peared; the oral skeleton has not yet appeared in this specimen, 

 c. b. ciliated band; Up. hydropore; i)r. I. i)rimary tentacle; tf. .. second pair of 

 tubefect. "-'Vi- 



3. Same larva, 2V2 days old; from the ventral side. The mouth opening has been formed. 

 Letters as in fig. 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 Ih'st ventral plate (v.) and the first side |)late with its spine have l)een formed. 

 'I'lie mouth shields have not yet apjieared. t. terminal plate. '-"^ ,. 



5. Longitudinal, frontal, section of larva of Ophioncreis squamiiloaa. 2(5 hours old; 

 e. c. enterococl; h. hydrocoel; st. stomach, ""/i- 



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

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

 enterococl 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 eclodernv. "7i- 



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

 side, in the skin of wliicli the primary jilates are observed, irregularly arranged. *"/!• 



Plate XXXII. 



All figures of ()pl)iiin(>tiis hrxaclis {l\. A. Smith). 

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



