Medusae of the world . Fig. 284.—Solmaris flavescens (Mgineta flavescens), afterGegenbaur, in Zeit. fur wissen. Zool., Bd. 8. —SOLMARIS. 435 and the same time, giving rise to a 16-cell stage. In any event, the cells of the upper (animal)pole usually divide so as to become smaller than those of the lower. No segmentation cavity isformed; but the superficial cells divide one after another and their inner-halves migrateinward to form a loose mass of cells which gives rise to the entoderm. The planula becomesoval in outline. The gallert forms a cap-like mass of gelatinous substance be
Medusae of the world . Fig. 284.—Solmaris flavescens (Mgineta flavescens), afterGegenbaur, in Zeit. fur wissen. Zool., Bd. 8. —SOLMARIS. 435 and the same time, giving rise to a 16-cell stage. In any event, the cells of the upper (animal)pole usually divide so as to become smaller than those of the lower. No segmentation cavity isformed; but the superficial cells divide one after another and their inner-halves migrateinward to form a loose mass of cells which gives rise to the entoderm. The planula becomesoval in outline. The gallert forms a cap-like mass of gelatinous substance between the ecto-derm and entoderm at the upper end of the larva. The exumbrella entoderm cells are small. Fig 28 t —Solmaris fiavescens, from life, by the author, at Naples Zoological Station, winter of 1907-08. A. Side view of mature medusa. B. Immature sensory-club. C. Fully-developed sensory-club. D. Tentacle. E. Stomach-margin show-ing female gonad. F. Diagrammatic section of medusa. and flat while those of the subumbrella entoderm are very high and large. The tentacles growout as wide basal bulbs from the margin and finally the bell grows out as a ring beneath andbetween the tentacle-bulbs. The mouth breaks through and the medusa is thus formed from the actinula. . The origination of the primitive, entoderm cells through division from the inner ends otthe superficial cells of the blastula recalls the condition observed in Liriope. 436 MEDUS-ffi OF THE WORLD. According to Maas, if the egg be cut into two when in the 2-cell stage, each cell finallydevelops into a small, normal planula and medusa. If the 8-cell stage be separated into a «
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