NARCOMEDUS.E — SOLMARIS. 433 



Haeckel founded this genus in 1879, establishing it for Solmaris godeffroyi from Samoa, 

 and other medusae; but the longest-known medusa belonging to this genus is probably " Poly- 

 xenia" leucostyla of Will, 1844, from the Mediterranean. 



GENERIC CHARACTERS. 



Solmaridae with a variable number of tentacles, alternating with an equal number of 

 marginal lappets. The gonad is ring-like, not composed of an annular zone of saccules in the 

 ectoderm of the subumbrella floor of the stomach. There are no peripheral stomach-pouches 

 extending outward into the lappets, but the outer margin of the stomach is simple and circular. 

 A marginal canal-system may or may not be present. Exumbrella sensory tracts may or may 

 not occur above the sensory-clubs. 



The outer margin of the stomach is usually simple, entire, and circular. When it displays 

 notches or a wavy outline these appearances are not caused by intertentacular pouches in the 

 lappets beyond the periphery of the central stomach. 



The genus Polycolpa Haeckel, 1879, appears to be composed of immature forms with a 

 simple, ring-like gonad around the periphery of the stomach and without peripheral stomach- 

 pouches. These medusae are probably the young of other forms of Solmaridae, possibly 

 Solmaris. 



Haeckel records Polycolpa zonaria, 12 mm. wide, with 10 to 12 lappets and tentacles, 

 60 to 90 sensory-clubs. Genital ring narrow, with a wavy outline, slightly convex in each 

 lappet. Color blue. Locality, Mediterranean. 



Polycolpa zonorchis, 16 mm. wide, 17 lappets and tentacles, 200 to 220 sensory-clubs. 

 Genital ring wide, swollen, developed upon the subumbrella floor of the outer two-thirds of the 

 lower wall of the stomach. Locality, Venezuela, South America. 



Polycolpa forskalii Haeckel, 1879, 1 88 1 , is evidently a Solmaris with a simple, ring-like 

 gonad. 



Anatomically speaking Solmaris may be regarded as the simplest and possibly phylo- 

 genetically the oldest of the Narcomedusae and the others may have been derived from it. 



Solmaris leucostyla Haeckel. 



Polyxenia leucostyla, Will, 1844, Hone Tergestina, p. 64, taf. 2, fign. 1-4, Leipzig. — Graeffe, 1884, Arbeit. Zool. Inst. Wien, 

 Bd. 5, p. 360. — MetschnikofF, E., 1886, Arbeit. Zool. Inst. Wien, Bd. 6, p. 254, taf. 23, fig. 29; 1886, Embryol. Studien, 

 an Medusen, Wien, pp. 23 (egg); 35 (segmentation); 64 (formation of entoderm), taf. 8, fign. 2-36. 



Solmaris leucost\lus, Haeckel, 1879, Syst. der Medusen, p. 357. 



Bell flat, about 3 mm. wide, 12 to 26 slender, solid, filiform tentacles, 1.5 times as long as 

 the bell-diameter. These tentacles project from the sides of the bell well above the lower 

 margin. 



Alternating with the tentacles are an equal number of marginal lappets each (usually) 

 with one marginal sense-club. Thus, in specimens found by MetschnikofF, one with 18 

 tentacles had 17 sensory-clubs; one with 26 tentacles, 33 clubs; and one with 25 tentacles had 

 17 marginal sense-organs. Velum small. Stomach flat, lens-shaped, without lateral pouches. 

 Mouth simple, closed. Gonad a wide ectodermal annulus in the subumbrella wall, around the 

 periphery of the stomach. Tentacle-tips and sense-organs faint green, other parts colorless. 

 Mediterranean, Messina, Villafranca, Naples, etc. It is quite common at Trieste, Adriatic, 

 according to GraefFe, from September to January. 



The early development of this medusa has been studied by MetschnikofF, 1886, and is quite 

 different from that of Solmaris flavescens, with which this form has often been confounded. 

 The egg is 0.127 to 0.147 mrn - wide and is laid between I and 3 in the afternoon, in March and 

 April, in the Mediterranean. Segmentation is total, but sometimes unequal, and then the 

 gastrula is formed by epibole. Sometimes, however, the segmentation is total and equal, and 

 then a solid morula is formed, the central cells of which become the entoderm. 



It is distinguished from the common Solmaris fiavescens, of the Mediterranean, only by its 

 small size when mature, its large number of tentacles, and few sensory-clubs. It is possible 

 that the two forms are mere varieties one of the other. 



