ABSTRACT
I Have for several years taken much interest in the reproduction of the naked-eyed Medusæ, and have endeavoured to obtain the polypoid larvæ of these creatures ; hitherto, however, with very indifferent success, having only succeeded in hatching two, Æquorea vitrina and Furris neglecta. Various species of Thaumantias swarm in the Firth of Forth, near Edinburgh, but when confined they almost invariably “cast” their ova, which never become developed into planuloid larvæ. This summer I have succeeded in obtaining the polyps in the following manner.
Three glass vessels, each containing about two gallons, were filled with clean sea-water, and carefully examined for two or three days. On the fourth day six individuals, two males and four females, of F. inconspicua were placed in one of the vessels. In a few days afterwards a considerable number of planulæ were found in this vessel alone, and were carefully removed with a glass syringe into a small vessel of filtered sea-water. Of these, two affixed themselves to the side of the vessel, and developed each a disc, branching into four symmetrical lobes, spreading over the glass. From the juncture of these lobes sprung the polyp-stalk, which put forth the polyp from its summit.
The polyp of T. inconspicua resembles very closely Cam-panularia raridentata, Alden, the stalk being ringed at its root and again just beneath the cell ; the cell toothed with seven denticulations. The polyp, with a trumpet-shaped mouth and fourteen alternating tentacles.
After a few days one of the lobes attached to the glass of one of the young zoophytes began to enlarge, and extended itself into a creeping fibre, from which a second polyp-stalk sprung. This stalk was crowned with a cell having nine denticulations, and its contained polyp had eighteen tentacles. The other young zoophyte also put forth a creeping fibre and second polyp in like manner, but its cell had only seven teeth and its polyp fourteen tentacles. At this stage both specimens died. In the meantime the planulæ in the larger vessel had covered the side of the vessel with a great number of young zoophytes, but none of these put forth a second polyp*.
Op. cit., livraison iii.
† Op. cit., livraison ii, p. 394.
‡ ‘Edinb. New Phil. Jour.,’ July, 1859.
