NARCOMEDUSiE — CUNOCTANTHA. 461 



GENERIC CHARACTERS. 



/Eginidae with 8 tentacles and 8 peronial furrows, alternating with 8 marginal lappets. 

 With 8 peripheral, uncleft outpocketings of the central stomach in the radii of the 8 tentacles. 

 A peripheral, peronial canal-system may or may not be present. Otoporpae are found in all 

 known forms of Cunoctantha. 



We should not attempt to separate families of Narcomedusae upon such a variable char- 

 acter as that of the presence or absence of the very degenerate peripheral canal-system. Also 

 the presence or absence of "sensory" tracts above the marginal clubs is apparently no more 

 important than the presence or absence of rows of nematocyst-cells over the exumbrella in 

 many Anthomedusae. It is safer to regard such slight differences as of specific, not of generic 

 value. Moreover, the otoporpae and peripheral canals may vary independently, and to consider 

 both of them as of generic value would introduce a complexity into the classification which 

 would cause closely related species to be widely separated, thus obscuring their actual rela- 

 tionship. It appears to me that the primary object of classification is to indicate genetic 

 relationships, rather than to emphasize distinctions. 



The larvae of the medusae of Cunoctantha are parasitic upon or within other medusae. 

 Thus C. octonaria infests Turritopsis nutricula and C. parasitica is parasitic upon or within 

 Geryonia. 



The development of these parasitic larvae has been studied by McCrady, F. Miiller, 

 Haeckel, Uljanin, MetschnikofF, Brooks, KorotnefF, Maas, Woltereck, and others, and will 

 be treated of more in detail in the descriptions of the species. A remarkable case of degener- 

 ation is that of Gastrodes parasiticum A. KorotnefF, 1888 (Zeit. fur wissen. Zool., Bd. 48, 

 p. 650, taf. 40, fign. 1 -8). This is parasitic within the mantle cavity of Sal pa fusifornns. It 

 has neither muscles nor nettle-cells, but is a double-layered, thimble-shaped "larva," with a 

 median supporting lamella, which forms a thick ring around the inverted margin. The 

 oesophagus is turned inward like that of an anthozoan. The egg-cells develop in the ecto- 

 derm and the animal appears to become mature without developing into a medusa. It is 

 inferred that this parasite is a degenerate Cunoctantha on account of its close resemblance to 

 the larva of Cunoctantha parasitica, which develops in the gastric cavity of Geryonia, and 

 finally produces free swimming medusae by asexual budding. 



One species, Cunoctantha fowleri Browne, produces medusa -buds asexually upon its 

 stomach-pouches. 



No sharp line of demarcation can be drawn between Cunoctantha, with its 8-rayed, free- 

 swimming medusa stage, and Cunina, in which the free-swimming medusa has more than 8 

 rays. Cunoctantha is indeed retained only for purposes of classification, its genetic affinities 

 being evidently very close to Cunina. 



Cunoctantha octonaria Haeckel. 

 Plate 55, figs. 1, i', and 2. 



Cunina octonaria, McCrady, 1857, Gymn. Charleston Harbor, p. 109, plate 12, figs. 4, 5; Proc. Elliott Soc. Nat. Hist. Charles- 

 ton, S. C, vol. I, plates 4-7. — Agassiz, L., 1862, Cont. Nat. Hist. U. S., vol. 4, p. 168. — Brooks, 1883, Studies Biol. 

 Lab. Johns Hopkins Univ., vol. 2, p. 467; 1S84, Zool. Anzeiger, Jahrg. 7, p. 710; 1886, Johns Hopkins Univ. Circular, 

 No. 49, p. 86. — Maas, 1893, Ergeb. der Plankton Exped., Bd. 2, K. c, p. 53. — Agassiz, A., and Mayf.r, 1899, Bull. 

 Mus. Comp. Zonl. at Harvard College, vol. 32, p. 166. 



Foveolia octonaria, Agassiz, A., 1865, North Amer. Acal., p. 51. 



Cunoctantha octonaria, Haeckel, 1879, Syst. der Medusen, p. 316. — Brooks, 1886, Mem. Boston Soc. Nat. Hist., vol. 3, p. 

 361, plates 43, 44. — Wilson, H. V., 1887, Studies Biol. Lab. Johns Hopkins Univ., vol.4, p. 95, plat" '~3> '9 figs. — Maas, 

 i892,Zoolog. Jahrb. Anat.Abth., Bd. 5, Heft 2, p. 274.— Bigelow, H. B., 1909, Mem. Mus. Comp. Zool. at Harvard 

 College, vol. 37, p. 52, plates 14, 15, and 17. 



Mature medusa (plate 55, fig. 1). — Bell about 7 mm. in diameter, flatter than a hemi- 

 sphere. 8 tapering tentacles, somewhat longer than bell-radius, project from sides of bell 

 about midway between margin and apex; these tentacles are stiff" and capable of but little 

 movement and are carried bent downward in scimitar-like curves. The entodermal core of 

 each tentacle consists of a row of disk-shaped, vacuolated cells. This core projects inward into 

 the gelatinous substance of the exumbrella, immediately above the middle of the outer edge of 



