LIFE-HISTORY OF MELICERTIDIUM 347 
5. Claus, C.—‘ Arbeit. Zool. Inst. Wien ’, Bd. 4, 1881, Heft 1. p. 589. 
6. Hartlaub.— Wiss. Meeres-Untersuch.’, Bd. 1, 1894, p. 192. 
7. Mayer, A. G.—*‘ Medusae of the World”, ‘ Public. Carnegie Inst. 
Washington ’, 109, 1910, vol. i, pp. 207-8. 
8. Metchnikoff, E.—‘ Embryologische Studien an Medusen’*. Wien, 1886. 
9. Romanes, G. I.—‘‘ An Account of some new Species, Varieties, and 
Monstrous Forms of Medusae ”’, ‘Journ. Linn. Soc. Zoology ’, vol. 12, 
1876, pp. 524-31. 
10. Stechow, E.—‘ Ein thecenloser Hydroid der mit einer Leptomedusa 
in Generationswechsel steht’, ‘Zool. Anz.’, Bd. 41, 1913, pp. 582-6. 
11. Wright, T. S.—‘‘ On the Reproduction of Thamantias incon- 
spicua’’, ‘Quart. Journ. Micr. Sci.’, vol. 2, 1862, pp. 221, 208. 
HXPLANATION OF PLATE 16. 
Figs. 1-15.—Development of Melicertidium. 
Figs. 1-7.—Stages in segmentation and blastula formation of the egg 
of Melicertidium. 
Figs. 8-11.—Change to the planula, formation of endoderm (end), &c. 
The arrow and circle between 9 and 10 indicate respectively the direction 
of progression of the larva, and its rotation as viewed from the narrow 
end. 
Figs. 12-18.—Fixation of the larva: formation of first tentacles. 
Fig. 14.—Stage with eight tentacles. 
Fig. 15.—Portion of a colony, (a) hydranth; (b) medusa ready for 
liberation ; (c) young hydranth and young medusa bud; (d) medusa 
bud almost fully grown; (e) hydranth fully stretched out; (/') young 
polypite arising from a hydrorhiza. 
Fig. 16.—Just liberated medusa. 
Fig. 17.—Aboral part of medusa, two weeks old, showing mesogloeal 
projection on summit of bell. 
Fig. 18, (a), (6), (c)—Stomach and radial canals viewed from above 
in two days, three weeks, and six weeks’ old medusae respectively, showing 
the formation, by interradial outgrowths from the stomach, of four new 
‘radial’ canals. 
Fig. 19.—Medusa, seven weeks old, showing interradial outgrowths from 
the stomach which have met corresponding upgrowths from the ring 
canal. R, one of the four original radial canals ; 1.R., one of the four new 
interradial canals formed in the manner described above. 
