SEMAEOSTOMEj?^ — PELAGIA. 



entoderm and these are quickly followed by another pair from the ectoderm of the throat- 

 tube, the two latter being 90° away from the former. The ectodermal pouches then give rise 

 each to two side branches and soon thereafter the entodermal do the same. Thus the cen- 

 tral stomach comes to have 12 radial pouches. 4 more radial pouches are soon formed 

 from the ectodermal pouches, so that the young medusa finally possesses 16 radial pouches. 

 It follows m adult medusa that the center of the exumbrella side of the central stomach is derived 

 from entoderm. 2 diametrically opposed, perradial pouches are ectodermal in origin and the 

 other 2 are entodermal. The 4 interradial pouches are ectodermal, and of the 8 adradial 

 pouches, 4 are ectodermal and 4 entodermal. The wall of the oesophagus is of ectodermal 

 origin. The 3'oung medusa soon develops 8 lobes which bifurcate, giving 16 marginal lap- 

 pets. The 8 marginal sense-organs develop before the tentacles. The mouth is at first a sim- 

 ple, round opening at the center of the crater-like ectodermal depression. It soon acquires 

 4 lips, but the mouth-arms do not develop until a later stage. It is probable that the ecto- 

 derm does not take so large a share in the formation of the stomach-pouches as Goette sup- 

 poses (see Chrysaora and Aurellia). 



Pelagia panopyra P^ron and Lesueur. 



Medusa panopyra, Peron et Lesueur, 1807, Voyage aui Terres Australes, planche 31, fig. 2. 



Pelagia panopyra, VtRos et Lesueur, 1809, AnnaLdu Mus. Hist. Nat., tome 14, p. 349. — Eschscholtz, 1892, Syst. der Acal., 

 p. 73, taf. 6, fig. 2. — Brandt, 1838, M<-ni. Acad. St. Petersbourg, tome 4, ser. 6, Sci. Nat., p. 382, taf. 14, fig. l; taf. 14 

 A, fign. 1-5. — Haeckel, 1880, Syst. der Medusen, p. 509 (literature). — Vanhoffen, 1888, Bibliotheca Zoologica, Heft. 3, 

 p. 14. — Fewkes, 1889, American Naturalist, vol. 23, p. 592, fig. 1; 1889, Bull. Essex Inst. Salem, vol. 21, No. 7, p. 122, 

 plate 5, fig. I. — Maas, 1903, Scyphomedusen der Siboga Exped., Monog. 1 1, p. 29. — M\yer, 1906, Bull. U. S. Fish Com- 

 mission, vol. 23, part 3, p. II 39, plate 2, figs. 3, 4. — Bigelow, H. B., 1909, Mem. Museum Comp.Zool. at Harvard College, 

 vol. 37, p. 43. — Maas, 1909, Abhandl. Akad. Wissen. Munchen, Suppl. Bd., 1 Abhandl. 8, p. 43. — Kishinouve, 1910, 

 Journal College Sci. Tokyo, vol. 27, art. 9, p. 9. 



The characters of this widely distributed Pacific form are described in the table under 

 the genus Pelagia. It is distinguished from the closely allied P. flaveola by its pink colora- 

 tion, whereas P. flaveola is yellowish. Moreover the nettle-warts of P. panopyra are low 

 and domelike, while in P. flaveola they are erect and bluntly pointed. 



Fig. 364. — Pelagia faveola, from Tahiti, after Agassiz and Mayer, in Mem. 

 Mus. Comp. Zool. at Harvard College. 



P. panopyra Is common off the coast of California and extends across the Pacific to the 

 Malay Archipelago, and northward to Japan. 



Vanhoffen gives the dimensions of a specimen as follows: Bell 27 mm. wide, 6 mm. high; 

 mouth-tube 15 mm. long; lips 27 mm. long. 



When young the medusa has onl)' 4 tentacles. When the bell is 15 mm. wide the gonads 



begin to develop. 



Pelagia panopyra var. placenta. 



Pelagia f)lacenta, Haeckel, 1880, Syst. der Medusen, p. 510. — Vanhoffen, 1888, Bibliotheca Zoologica, Bd. i. Heft. 3, p. 12, 

 taf. 6, fig. 20. 



This appears to be a very close variety of P. panopyra. Both medusae are widely dis- 

 tributed over the tropical Pacific. See synoptic table of forms of Pelagia. I believe that this 



