434 



MEDUSAE OF THE WORLD. 



Solmaris flavescens. 



Pachysoma flavescens, Koluker, 1853, Zeit. fur wissen. Zool., Bd. 4, p. 322. 



Miineta flavescens, Gf.genbaur, 1856, Zeit. fur wissen. Zool., Bd. 8, p. 263, taf. io, fig. 9. 



Polyxenia flavescens {non kucostyla), Metschnikoff, E., 1874, Zeit - fur wissen - Zool -> Bd - 2 4> P- 22 > uL S> 4- 



Solmoneta flavescens, Haeckel, 1879, Syst. der Medusen, p. 353. 



( ?) Cim/na discoides, Fewkes, 1881, Bull. Museum. Comp. Zool. at Harvard College, vol. 8, p. 161, pi. 2, fig. 8; pi. 4, fags. 1,2. 



Solmoneta flavescens, Maas, 1893, F.rgeb. der Plankton Expedition, Bd. 2, K. c., p. 47. 



,£»,«<* (Solmoneta) flavescens, Maas, 1902, Sitzungsber. Gesell. fur Morphol. und Physiol. Miinchen, Bd. 17, p. 14, fign. 1-18 



(early development).— 1908, Verhandl. deutsch. Zool. Gesellschaft, p. 124, fig. 7 (structure of the egg.) 

 Solmoneta flavescens, Maas, 1904, Result. Camp. Sci. Prince de Monaco, fasc. 28, p. 41. 

 M^ineta (Solmoneta) flavescens, Stschelkanowzeff, 1905, Nachr. Gesell. Freunde Naturw. Moskau, Bd. 1 10, p. 30, taf. 3, fign. 



1-22; 1906, Zoolog. Centralblatt, Bd. 13, p. 678 (embryology). 

 Non Solmaris flavescens, Vanhoffen, 1908, Narcomedusen "Faldivia" Expedition, p. 58. 



Flat and lens-shaped, 15 to 23 mm. in diameter. The gelatinous substance of the central 

 disk is lenticular and quite thick, but the sides of the bell are thin, flexible, and vertical and 

 constitute the marginal bell-lappets, or "bell-collar" of Haeckel. 12 to 17 (usually 13 to 15) 

 long, stiff tentacles stand out at right-angles to sides of bell and are capable of but little 

 movement; their proximal ends are inserted into the sockets in the thick gelatinous substance 



of the bell just above the stomach. The 

 tentacles are about as long as the bell- 

 diameter. Immediately beneath each ten- 

 tacle and extending radially across the thin 

 outer part of the bell between the lappets, 

 is a thickened, solid, rib-like strand of ecto- 

 derm called the peronium. Thus in a 

 medusa having 14 tentacles there are 14 

 peronia; they give support to the tentacles 

 which arise just above them. The mar- 

 ginal lappets alternate with the tentacles 

 and are therefore equal in number to the 

 latter. There are 2 to 3 sensory-clubs 

 (usually 2) upon each lappet. Each club 

 contains 2 garnet-colored spherical ento- 

 dermal concretions, one being large and 

 the other small. The club itself is elon- 

 gate, mounted on a slender stalk and is 

 covered with bristles. There are no oto- 

 porpae. The velum is large and powerful 

 and capable of much distension and con- 

 traction. Sections cut by me and stained in Delafield's haematoxylin show that there are 

 no peronial canals and" no ring-canal. Stomach flat and lenticular, mouth is a simple, round 

 opening; periphery of stomach circular. The gonad is developed in the ectoderm of the 

 subumbrella floor of the stomach-margin. The gonads and tentacle-tips are milky to golden- 

 greenish, the entoderm of the stomach being lighter. All other parts are perfectly trans- 

 parent, excepting the concretions of the sense-clubs, which are port-wine colored. 



This medusa is abundant in the Mediterranean, where it swims languidly near the surface. 

 Among 20 specimens studied from life by the author during the winter of 1907-08, at 

 Naples, 2 had 12 tentacles, 4 had 13, 6 had 14, 4 had 15, 2 had 16, and 2 had 17 tentacles. 



This form bears some resemblance to Solmaris kucostyla, which also occurs in the Mediter- 

 ranean but Maas, 1902, has shown that its development differs from that of Solmaris kuco- 

 styla as described by Metschnikoff, 1886. "S. flavescens" of Vanhoffen, 1908, appears to 



be a Solmtssus. . 



According to Maas, 1902, in S. flavescens the egg is fertilized in the water after being 

 dehisced from the ovary. It is opalescent, whitish, and 0.8 to 1.5 mm. in diameter. The first two 

 cleavages are meridional and give rise to 4 equal blastomeres. The third cleavage is equatorial 

 and may result in 4 small and 4 large blastomeres, or in 8 equal blastomeres. When the cleav- 

 age results in 4 small and 4 large blastomeres, the 4 small ones divide more rapidly than the 4 

 large, giving a 12-cell stage; but where the 8 blastomeres are equal they divide again at one 



Fig. 



284.— Solmaris flavescens (Mgineta flavescens), after 

 Gegenbaur, in Zeit. fur wissen. Zool., Bd. 8. 



