ILLUSTllATIONS xxix 



FIO. . PAGE 



360. Lateral views of an advanced Bipinnaria of Aslerias vulgaris in whicli tlie 



brachiolarian arms are just appearing ..... 468 



361. "Ventral view of a Bipinnaria of Asterias vulgaris, of the same age as that 



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

 cavities ......... 469 



362. Lateral views of the brachiolarian phase of the larva of Asterias vulgaris 



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



363. Frontal longitudinal sections of two early embryos of Asterina gibbosa in 



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



364. Views of a free-swimming larva of Asterina 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 siife 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 progre,ss 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 Solaster endeca . . . 482 



373. Early stages in the development of Op/i.iottriK/j-ag'iKs . . . 485 



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



375. Ventral views of young larvae of Op/aoiAria/rajriKs . . . 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 fragilis up to the end of the first period of metamorphosis . 493 



378. Longitudinal frontal section of a larva of Ophiothrix fragilis 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 . . . . . .497 



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 Ophiura brevis during the metamorphosis . 502 



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



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

 course) ......... 50/ 



384. Early stages in the development of Echinus esculentus . . .508 



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



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



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

 epaulettes . • ■ • • ■ • . . 510 



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



from the dorsal surface . . • ■ • .512 



