C02 E. W. MACBRIDE. 



YiG. 9. — Dor&al view of a larva, five days old, reared from natural fcrlilisatioii. 

 Tlic cocloriiic vet^iclc is coni|)lctcly divided on bolli sides iuto anterior and 

 posterior halves. »/.;;. Primary madreporic pore, x 200. 



¥iG. 10. — Dorsal view of a larva, six days old, reared from natural fertilisa- 

 tion, p.d. Rudiments of postero-dorsal arms. r. hy., I. hy. lludiments of rii^'lit 

 and left liydrococles respectively. X 2G0. 



Fig. 11. — Dorsal view of a larvn, eii,'lit days old, reared from natural 

 fertilisation. The postero-dorsal arms have acquired a fair length, x 150. 



PLATE 32. 



Fig. 12. — Ventral view of a larva, sixteen days old, reared from aitificial 

 fertilisation. All the arms have attained their full length. 1 — 5. Lobes of the 

 left hydrocoelc, which has grown forward beyond the left anterior ccelom. 

 X 150. 



Figs. 13 a and b. — Dorsal and ventral views respectively of a larva picked 

 out of Plankton, in which the metamorphosis is just beginning. The ])re- 

 scrvative has dissolved out the larval skeleton. 1 — 5. Lobes of the left hydro- 

 cuile, which is beginning to extend ventrally under the oesophagus ; I — IV. 

 lludiments of three of the arms of the adult brittle-star. int. Intestine. 

 st. Stomach, slom. Stomodajum. x about 100. 



Fig. 11. — Ventral view of a larva picked out of Plankton, in which the 

 metamorphosis is more advanced than in the {)receding figures. The prejiara- 

 tion was somewhat opaque, and the larval skeleton has been dissolved by the 

 preservative. Observe that the left antero-lateral arms and lobes 1 and 2 of 

 the left hydrocoelc have passed over the oesophagus, x 100. 



Fig. 15. — Ventral view of a larva twenty-three days old, reared from arti- 

 ficial fertilisation, in which the metamorphosis is very far advanced. All the 

 larval arms except the postero-lateral are reduced in size. az. t. The terminal 

 tentacle of one of the radial water-vascular canals, b. t. Buccal tentacle. 

 X 100. 



I'lG. 10. — Ventral view of a larva of the same age as foregoing, but of more 

 advanced development, reared from artificial fertilisation. All the larval arms 

 except the postero-lateral arms have disappeared ; the developing adult arms 

 are bent over the disc. The spines of the mouth-angles {sp.) have made their 

 appearance. X 100. 



FiG. 17. — Ventral view of a young briUle-star which has just completed its 

 metamorphosis. Artificial fertilisation, twenty-six days. pi. The calcareous 

 lod of one of the two postero-lateral arms which have now disappeared. The 

 hooks characteristic of the breidiic stage of Uphiothrix fragilis arc seen 

 attached to the sides of the arms. X 100. 



Fig. 18. — Section of a segmenting egg. Artificial fertilisation. X 500. 



