68 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



to swim through the water with great rapidity. 16 diverticula; or pouches 

 from the stomach enter the 16 lappets. Each of these pouches is simple, 

 and does not give rise to any system of canals ramifying through the lappets. 

 The mouth is a simple cruciform opening and there are no oral appendages, or 

 palps. The gastro- vascular cavity is a wide space occupying the whole centre 

 of the umbrella and extending outward into the lappets to form the 16 lappet- 

 pouches. There are 4 groups of gastric cirri, situated in such manner that the 

 2 diameters passing through them are 45° apart from the 2 diameters passing 

 through the cross formed by the lips of the mouth. All 4 of these diameters 

 pass through the marginal sense-organs. There are about 6 tentaculse in each 

 group of gastric cirri, thus making in all about 24 gastric tentaculse. The 8 

 gonads are of entodermal formation, and are found in the 8 tentacular radii. 

 As Glaus, 1883, has shown, each one is formed from a pocket-like fold of the 

 entoderm. A band of circular muscles is found in the ectoderm of the sub- 

 umbrella, and radial muscle fibres run out from this band into the 16 marginal 

 lappets. The color of this medusa is quite variable. The gelatinous substance 

 of the bell is usually bluish white or brownish. The gonads are brownish red or, 

 in the case of the males, bright yellow rosin-colored pigment spots are found 

 in the ectoderm of the ex-umbrella, especially upon the lappets. These rosin- 

 colored spots are due to small crystals (see Glaus, 1883; Figure 44, Taf. VI.). 



A young ephyra of this species (see Figures 67, 68; Plate 23) was found 

 by us near Flamingo Key, Bahama Islands, Feb. 9, 1893. It was 2 mm. 

 in diameter. There were as yet no marginal tentacles. The otocysts each 

 contained 5-6 oval otoliths. There were only 4 gastric cirri. A slightly older 

 ephyra has been figured by Glaus, 1883 ; Figure 48, Taf. VII. 



This medusa is common in the Mediterranean, and is also found among 

 the Bahama and Tortugas Islands. It was described by Vanhoffen, 1893, from 

 near the mouth of the Amazon River. A very closely allied species was found 

 by us in the Fiji Islands, Pacific Ocean. 



LINERGES, Haeckel, 1880. 



Linerges mercurius, Haeckel. 



Linerges mercurius, Haeckel, E., 1880, Syst. der Medusen, p. 495, Taf. XXIX. 



Figs. 4-6. 

 Linerges pegasus ? Haeckel, E., 1880, Syst. der Medusen, p. 495. 



Vast numbers of ephyrse of this medusa are found among the Bahama 

 Islands and along the Florida Goast in March ; and the mature medusae are 

 very abundant in June. At times these creatures appear in such numbers that 

 himdreds are captured in every haul of the tow net. They congregate in 

 great windrows, remain abundant for a few days, and then disappear for an 

 indefinite period. 



