ILLUSTRATIONS xxix 



360. Lateral views of an advanced Bipinnaria of Axt< r//s rii/i/nris in which the 



brachiolarian arms are just appearing ... . 468 



361. Ventral view of a Bipinnaria of Asterias rult/ta-is, of the same age as that 



shown in Fig. 360, in order to show the mutual relations of the coelomie 

 cavities ......... 469 



362. Lateral views of the brachiolarian phase of the larva of Asterina rn/i/itris 



in various stages of fixation and metamorphosis .... 470 



363. Frontal longitudinal sections of two early embryos of Asterinn gibbosn in 



order to show the development of the, coelom .... 473 



364. Views of a free-swimming larva of As/cri/ia gibbosa, five or six days old . 474 



365. Longitudinal frontal sections of larvae of Asterina gibbosa in order to 



show the segmentation of the coelom and the origin of the hydrocoele 



and madreporic vesicles ....... 475 



366. Longitudinal frontal sections of larvae of Asterina gibbosa, seven to eight 



days old, in order to show the beginning of the metamorphosis . . 476 



367. Views from the side of a larva of Asterina gibbosa, seven days old, in the 



initial stages of metamorphosis ...... 477 



368. Views from the side of a larva of Asterina gibbosa, eight days old, showing 



further progress in the process of metamorphosis .... 478 



369. Longitudinal frontal section through a larva of Asterina gibbosa about the 



same age as those shown in previous figure .... 478 



370. Dorsal (i.e. aboral) views of two young specimens of Asterina gibbosa 



shortly after the metamorphosis ...... 479 



371. Three figures illustrating the development of the genital stolon, genital 



rachis, and gonad in Asterina gibbosa ..... 480 



372. Longitudinal frontal section of the larva of Solastcr endeca . . . 482 



373. Early stages in the development of Ophiothri,'- fragifis . . . 485 



374. Longitudinal frontal sections of early larvae of Ophiothrix fragilis . 486 



375. Ventral views of young larvae of Ophiothrix fragilis . . . 488 



376. Ventral view of fully developed larva of Ophiothrix fragilis, sixteen 



days old .... .... 489 



377. Three diagrams illustrating the internal changes which occur in the larvae 



of Ophiothrix frayilis up to the end of the first period of metamorphosis . 493 



378. Longitudinal frontal section of a larva of Ophiothrix frayilis in the first 



stage of metamorphosis . . 494 



379. Two larvae of Ophiothrix fragilis in the concluding stages of metamor- 



phosis, viewed from the ventral side ..... 496 



380. Transverse sections through the discs of two young brittle-stars in order to 



show the origin of the germ cells ... . . 4'.i7 



381. Two diagrams designed to elucidate the mutual relationships of stone- 



canal, dorsal organ, axial sinus, madreporic vesicle, genital rachis, etc., 



in an Asteroid and an Ophiuroid respectively .... 500 



382. Ventral view of the larva of o/i/iiurn brcvis during the metamorphosis . 502 



383. Two stages in the segmentation of the egg of Strongyloeentrotus lividus. 



(The segmentation of the egg of Echinus esculcntus pursues an identical 

 course) .... . 507 



384. Early stages in the development of Echinus esculent us . . 508 



385. Young larvae of Echinus esciihntits, viewed from the dorsal surface . 509 



386. Echinopluteus larva of Echinus esculcntus, about eleven days old, viewed 



from the dorsal surface, in order to show the formation of the ciliated 

 epaulettes ... .510 



387. Echinopluteus larva of Echmus esculentus, twenty-three days old, viewed 



from the dorsal surface . . . .512 



