18 MEMORIAL PAMPHLET SHOWING CERTAIN DRAWINGS 



the nerve-cord extend outward from the 8 peronia to the sense-organs upon the bell-margin. 

 These 8 loops are put into connection one with another by means ot nerve tracts that run 

 through the peronia. Thus the nervous system consists of an 8-lobed, star-shaped ring ot 

 ciliated ectodermal cells situated upon the exumbrella (see plate 55, figs. I and 2, n, ) 



In the adult medusa there are typically 24 marginal sense-organs, 3 in each octant of the 

 bell, although occasionally there are as few as 2 or as many as 5 in an octant. Each sensory 

 club is situated upon a small, hemispherical elevation of the bell-margin called the sensory 

 cushion. The sensory cushion is formed from the cells of the nerve-cord, which at this place 

 are elongate and spindle-shaped and bear long delicate bristles. Centripetal to the sensory 

 cushion, on the exumbrella surface of the bell, there is a small, elliptical, elevated ridge, the 

 otoporpa, composed of a single layer of cube-shaped ectoderm-cells and containing a number 

 of nematocys'.s (see plate 55, figs. I and 2, o). The sensory-club is rod-like and cylindrical 

 and is attached to the sensory cushion by means of a short, narrow neck (see plate 55, fig. i')- 

 Each sensory-club contains two concretions that are situated within the entodermal core of 

 the club. The proximal otolith is small and spherical, while the distal is large, flat, and 

 crystalline. 



The velum is more complex than in most hydromedusae, for it consists not only oi a simple 

 annular membrane (see plate 55, figs. I and 2, v) that serves to partially close the opening of 

 the bell-cavity; but in addition it extends upward as 8 A-shaped webs between the 8 loops of 

 the nerve-cord (see plate 55, figs. I and 2 i 1 '), and thus it is that, morphologically speaking, the 

 margin of the exumbrella is bounded by the nerve-cord and hence the true form of the disk is 

 to be considered as an 8-rayed star, although the thin webs of the velum stretched between the 

 rays give it the appearance of a hemispherical bell. 



Manubrium cone-shaped and there are 4 perradial, cruciform lips. 8 gastric sacs radiate 

 outward from the central stomach-cavity, each sac being found in a tentacular radius. There 

 are no radial-canals and no ring-canals in this species. The gonads are developed in the ecto- 

 derm of the subumbrella immediately beneath the 8 gastric sacs. 



The medusa is colorless with the exception of a delicate sage-green tinge of the entoderm 

 near the lips and occasionally in the tentacles. 



Genus PELAGIA Pe"ron and Lesueur, 1809 

 Pelagia noctiluca P^ron and Lesueur. 



Medusa ao.'tiluca, FORSKAL, 1775. IV-mpt anim. itin. orient., p. 109. 



Pelagia r.o-nlura, PERI N u I.i M EUR, iSoq. Anna!, ilu Mus. Hist. Nat., turn.- 14. p. ;<;o; /'. furf,u,.i, Aurcllia pkosphorira, 

 I'-. . ,it.. pp. -,50, 358. KROHN. 1855, Mullen's Archiv. Anat. Physio!., p. 491, taf. 20 (development). HAECKEL, 1880, 

 s\ t. der Mc-d.is-n.p. 505 (list of authors and names). KOWALKVSKV, iS-;, Mem. Imp. Soc. Lovers of Nat. Hist.. Moscow, 

 vol. io. pan :. p. -. plate 3 (development). HAMANX, 1883, Zeit. fur \vissen. Zo..l., Bd. 38, p. 422, taf. 32 (development 

 and structure of gonads). METSCHNIKOFF, 1886, Embrvol. Studien an Medusen, \Vi.-n., p. 24 (egg); 67 (segmentation); 

 ico (larva); taf. 10, fu;n. 23-28. MONACO, Prince of, 1887, Comp. Rend. Paris, tome 104, p. 452 (swarming habits of 

 the medusa). V^XKOFT FN-, iSSS, Bibliotheca Zoologica, Heft. 3, p. 8, taf. I, fi.cn. 5, 6; taf. 6, fign. 1-5; 1908, Deutcch. 

 Sudpclar Expedition, 1901-1903, Bd. io, Zool. 2, p. 38. GOETTE. 1893, Zeit. fur wissen. Zoo]., Bd. 55, p. (-59. n fign., 

 taf. 30-31; 189}, Sirzunsslfcr. Ak.id. Wissen. Berlin, p. 853 (development). SCHAXEL, 1910, Zool. Anzeigcr, BJ. 35, p. 

 407 (histology of cbgcnesis). 



The following is a description of a typical, adult specimen from the Bay of Naples: 

 Disk somewhat higher than a hemisphere when contracted, but flatter than a hemisphere 

 when expanded. In ordinary contraction it is about 49 to 55 mm. in diameter and 31 mm. 

 high. Sides of bell relatively straight and sloping, the apex flat. Numerous nettle-wans 

 over the exumbrella, arranged in more or less irregular lines radiating trom aboral apex of 

 exumbrella. These warts are rich orange-red in color and are elongate and linear, some- 

 times with, but more often without, cross-foldings. Near the bell-margin, however, they 

 lose their linear shape and become small, simple, and more or less oval. 



The 8 marginal sense-organs are set in deep niches in the perradii and interradii. The 

 sense-club has no ocellus, but contains only a terminal mass of deeply pigmented orange-colored 

 crystalline concretions of entodermal origin. There is no sensory pit in the exumbrella above 

 the sense-club. The 8 hollow, tapering tentacles are each about twice (115 mm.) as long as 

 the bell-diameter. 



