LEPTOMKDUS/E PTYCIIU< MA \. - 1 ."> 



Ptychogena lactea A. Agassiz. 



Ptychogena lac tea, AGASSIZ, A., 1865, North Amor. Acal., p. 137, figs. 220-224; 1888, Bull. Mus. Comp.Zool.at Harvard College, 

 vol. 15, p. 128, fig. 422. HAECKEI., 1879, Syst JIT Mcdusen, p. 147. BROWNE, 1907, Annals anJ Mag. N.it. Hi ' .MT. 7, 

 vol. 20, p. 473. 



Ptychogena fiinnulata, HASCKF.L, 1879, Syst. Jcr Meduscn, p. 148; 1881, Rrport on Dccp-sea Medusa-, Report^ H. M. S. Chal- 

 lenger Zool., vol. 4, part ] 2, p. 7, plate 2, figs. 1 lo 8. LEVINSEN, 1893, Vid.Meddel. Nat. Fur. Kjcbtnhavn, ser. 5, Bd. 4, 

 p. 145. GRUNBLRG, 1898, Zoolog. Jahrb., Abth. Syst., Bd. 11, p. 465. 



Plychogrna finnulata var. intermedia LINKO, 1904, Zool. Anzeiger, Bd. 28, p. 217. 



Adult medusa. Bell about 50 to 70 mm. in diameter and 20 to 30 mm. in height. Sides 

 ot bell flange slightly outward. The gelatinous substance is about 10 mm. thick at aboral pole 

 of bell, but diminishes constantly in thickness towards the margin. Substance of" bell trans- 

 parent, but quite rigid. There are more than 300 long, slender, highly contractile tentacles, 

 with hollow, finger-shaped basal bulbs. When expanded these tentacles are about as long 

 as the bell-diameter. Their free extremities often become entangled and this causes the 

 tentacles to droop in graceful festoons from the hell-margin. There are 25 to 200 or more 

 marginal sense-clubs. They arise on the inner (centripetal) side of the tentacle bases near 

 the origin of the velum. These sense-clubs are elongate and pynform, with a narrow basal 

 stalk. They are between a third and a half as long as the basal bulbs of the tentacles. 

 Each sense-club is hollow and connected with the lumen of the circular canal. In some 

 places the sense-clubs are as numerous as the tentacles and often alternate with them in 

 position, but on other parts of the bell-margin they are much less numerous than the tentacles. 

 Velum very wide and thin. The 4 radial-canals are wide near their proximal ends, ad|acent to 

 manubrium, but straight and narrow near the circular vessel. These radial-canals are pin- 

 nated in their proximal halves, adjacent to the stomach. In this region they give rise to about 

 20 to 30 blindly ending, pinnate side branches, upon which the sjenital organs are situated. 

 The genital organs consist of leal-shaped sacs attached to the side branches of the radial- 

 canals. The free outer edges of these sacs are serrated or split up into a number of finger- 

 shaped points. Thus each genital gland consists of 20 to 30 leaf-shaped sacs or lamellae, all 

 connected with the main axis of the radial-canal. Manubrium wide and shallow. The 4 corners 

 of the fundus of the stomach are prolonged into 4 conical tunnels, whose ends extend to the 

 middle of the genital organs and occupy the proximal halves of the 4 radial-canals. Mouth- 

 opening quadrate and about one-third as wide as bell-diameter. Lips irregularly trilled and 

 extend at the 4 radial corners into 4 short, wavy, oral lobes. 4 narrow, ciliated grooves extend 

 along umbrella wall of the 4 radial-canals and meet at center of stomach on gastral surface of 

 gelatinous umbrella, forming a cross. The gonads and tentacle-bulbs are milk)' in color and 

 the marginal sense-clubs are white. All other parts of the medusa are transparent. 



This medusa appears to be an Arctic form. It was first found by A. Agassiz swimming at 

 considerable depth in Massachusetts Bay. Since then specimens have been described by 

 Haeckel, under the name of Pt\clws>t-ii<i pinuuliita, from the North Atlantic Ocean between 

 Ireland and Iceland (lat. 50 f N., long. 13 32' W. from Greenwich). The Challenger also 

 dredged a specimen between 1,250 fathoms and the surface near Halifax, Nova Scotia. Lev- 

 insen, 1893, records this medusa from Jakobshavn and Ritenbenk on the west coast of 

 Greenland, and Linko found it in Barents Sea in 72 30' N. lat., both in the eastern and west- 

 ern parts of the sea north ot Lapland. 



I believe that P. fiiiniilntii of Haeckel, 1879, is identical with P. luitea of A. Agassiz, 1865. 

 Upon comparing Agassiz's original figures (some of them unpublished) with those of Haeckel, 

 it appears that the only difference which may exist between the two forms is that in /'. piiinu- 

 l/itii the free, outer edges of the leaf-like gonads are serrated, whereas in P. Inctea of Agassiz 

 they appear to be entire and smooth. Also in Agassiz's figures some of the side branches of 

 the radial-canals give rise to secondary branches, and this appears not to be the case in 

 Haeckel's /*. fiiniulntn. Agassi/.'s specimens were, however, larger than those described 

 by Haeckel, and probably they may have been more matuu-. 



Linko, 1904, found a medusa in Barents Sea which he considers to be intermediate 

 between P. Itiftfd and P. pinnulutu, but nearer to I', finnulata. 



It is possible that this medusa is an inhabitant ot the deep-sea and that it comes to the 

 surface only occasionally. 



