46 



ACALEPII/E. 



Fig. 13. 



loosely attached to the lower surface of the 

 air-bladder. In the diphyda, they are in the 

 form of numerous vesicles, having thick tunics 

 filled with an opaque white fluid, and situated 

 within one of their swimming organs. Such 

 parts were seen by Eschscholtz only in some 

 individuals, and on this account he was dis- 

 posed to regard them as ovaries. But Messrs. 

 Quoy and Gaimard seem to consider it more 

 probable that the minute botryoidal bunches of 

 vesicles, which surround the base of each 

 sucker on the lengthened filaments, (before 

 alluded to as being subservient both to nutri- 

 tion and to locomotion,) are the ovaries.* 

 It does not appear that 

 either Eschscholtz or 

 Messrs. Quoy and Gai- 

 mard saw the ova. 



In the ciliograda, the 

 ovaries are more obvious. 

 They consist of two or 

 four vesicular organs, 

 each placed between two 

 of the cilia-bearing arches. 

 In cydippe, they are of a 

 red colour, and nearly cy- 

 lindrical shape. The ova 

 are spherical. 



The parts in the pul- 

 mograda corresponding to 

 the organs just referred to, 

 are eight round bodies, of 

 small size, situated near 

 the margin of the disc, 

 each formed of a vesicle, 

 containing, at its free ex- 

 A portion of the treraity, many minute 

 ovtgerous filament hexagonal corpuscules ; 

 of Diphyes much there is aUa ched to each 

 magnified. vesicle a digitated appen- 



dix, which seems to be hollow, and to com- 

 municate with the circular vessel. These 

 organs were seen by Gaede and by Muller 

 in medusa capillata, and M. aurita, and by 

 Eschscholtz in some species of cyanea, st/ie- 

 nonia, pelagia, and chrysaora ; Dr. M. Ed- 

 wards has observed them also, at certain 

 seasons, in rhizosloma ; and in carybdea mar- 

 supialis, he found, midway between each 

 pair of pendent filaments, and immediately 

 above a little notch in the margin, four 

 spots of a deep brown colour, each of which 

 appeared, under the microscope, to be formed 

 partly by a minute spherical body, having a 

 granular aspect, as if it were filled with eggs, 

 and partly by a little sac, with puckered sides, 

 which is imbedded in the gelatinous substance 

 of the body. These he regards as the ovaries.f 

 But, notwithstanding their having found gra- 

 nular bodies like ova in the organs above 

 described, neither Gaede nor Muller considered 

 them as ovaries. Muller regarded the granules 

 as excrementitious matters ; and Gaede thought 

 that he saw the ovaries in the plaited mem- 

 branes of the gastric cavities; whence he 

 observed the ova descend into certain minute 



* Ann. des Sc. Nat. x. 8. 



t Ann. des Sc. Nat. xxviii. 250. 



vesicles imbedded in the margins of the arms- 

 lie remarked that, in medusa aurita, when the 

 cells in the arms were filled with eggs, the 

 plaited membranes had none : and, on the other 

 hand, when there were no eggs in the arms, the 

 plaited membranes were studded with them. 

 Cuvier was also of opinion that the ova are 

 formed in the plaited membranes above men- 

 tioned, and that they are matured in the mar- 

 gins of the arms.* 



No observations, so far as we know, have 

 hitherto been made on the development of the 

 ova ; but Dr. Grant has recently stated that the 

 ova of equorea are furnished with cilia, and 

 have locomotive powers, like the ova of the 

 porifera and polypifera.^ The colours of the 

 acalephse often depend on the tints of their ova: 

 these are generally red, but sometimes brown, 

 yellow, or purple. 



VIII. Geographical distribution. We con- 

 ceive that a brief notice of this part of their 

 natural history may, in some measure, illus- 

 strate the physiology of the acalephae. They 

 are met with in all seas ; but certain families 

 exist more abundantly in some localities than 

 in others. The ciliograda and pulmograda, 

 for instance, are inhabitants chiefly of the colder 

 regions, while the physograda are seldom 

 found beyond the limits of the tropical zone. 

 Some float in bays, and near land, but the 

 greater number in the high seas. Medusa: and 

 cyanea are met with only in the cold and tem- 

 perate zones of the northern hemisphere. Cy- 

 dippe lives in the North Arctic Ocean, as well 

 as in the Pacific, under the equator. One species 

 of cestum inhabits the Mediterranean, another 

 the South Sea. It frequently happens that 

 enormous numbers of one species are met with 

 closely grouped together, so as somewhat to 

 impede a ship's progress for two or three suc- 

 cessive days ; after which, not a single indi- 

 vidual of the same species is seen. In the 

 European seas, it is chiefly in summer and 

 autumn that the acalephae swim on the surface. 

 In winter, they probably sink to the bottom. 



BIBLIOGRAPHY. Madeer, Tentamen systematis 

 Medusarum stabiliendi, in Nova Acta Aca '. Natur. 

 curios, vol. viii. Append, p. 19 ; and Papers in the 

 Svenska Vetenskaps nya Handlingar An. 1791, 

 transl. into Germ. s. t. Neue Abb. and. der Schwed. 

 Akademie, &c. Jahr 1791 ; Seite 75, 149, 227. 

 Dana, De quibusdam urticae marinae differentiis : 

 Miscel. Societal. Taurinens. v. iii. p. 206. Muller, 

 Beschreibung zweier Medusen : Beschaeft. der Ber- 

 liner Gesellsch. Nalurfor. Freunde Bd. 2. S. 290. 

 Cuvier, Sur 1'organization de quelques Meduses ; 

 Societe Philomat. A. 3, F. 2, p. 69. Strom, A 



gaper in Danish on the Medusa palliata in the 

 krifter der Kiobenhab. Selskabs nye Saml. Deel. 3, 

 S. 250. Swartx, Medusa pelagica beskrifven : 

 Svenska Vetens. Acad. Hand. A. 1791, S. 188 in 

 the German transl. T. 1791, S. 172. Gaede, Bey- 

 traege zur Anatomic und Physiologie der Medusen, 

 8vo. Berl. 1816. Quoy et Gaimard, Zoologie d'un 

 Voyage autonr du Monde, 2 vols. 4to. Atlas fol. 

 Paris, 1824. Duperrey, Voyage autour du Monde 

 4to. Atlas fol. Paris, 1826-1834. 



(John Coldstream.) 



* Regne Animal, second edit. iii. 277. 

 Carus, Comp. Anat. ii. 307. 

 t Lectures, Lancet, No. 565. p. 483. 



See also 



