174 .M 101)1 S.K OK THK WORLD. 



medusa is very abundant in autumn and winter along our Atlantic coast near the mouths 

 of large hays into which pure ocean water has free access. It is not usually found in brackish 

 water far from the ocean. It is found at Woods Hole, Massachusetts, and is common in Long 

 Island Sound as far west as New Haven; in the mouth of the Chesapeake; in Pamlico Sound, 

 especially near the inlets, and in the mouths of all southern harbors, in winter, as far south 

 as Fernandina, Florida. It is also found off the coast in the ocean. It has not been seen 

 north of Cape Cod, nor upon the southern Florida coast. Very often the medusa is seen 

 with all of its marginal tentacles broken off short, leaving only rounded stumps, this condition 

 being commonly found in animals living in brackish water or far from the ocean. N. " hetero- 

 iifnui" HaeckeJ, 1879, appears to be identical with our American TV. b/ichei. 



HyJronl <inJ young medusa. McCrady, 1857, is mistaken in his identification of the 

 hydroid of this medusa, for his hydroid is Margelopsis, The hydroid stock was found by 

 Brooks, 1883, in Newport River, North Carolina, growing upon a piece of submerged wood. 

 It is a Bougainvillia. The stems oi the hydroid are about 25 mm. in height. Each mam 

 stem gives rise to 3 or 4 short alternating branches, and these as well as the main stem end in 

 hydranths, which are sharply separated from the stem by means of a fold or collar. The 

 stems are covered by a thin, transparent, horny ectosarc which extends almost, but not quite, 

 up to the basal collar of the polypites. There are 2 or 3 irregular annulations upon the ectosarc 

 of the side branches, close to the mam stem. Each polypite bears 24 long, slender tentacles, 

 which arise in a single circlet near the distal end of the hydranths. The mouth is situated 

 at the extremity of a well-developed proboscis which is tunnel-shaped and sharply distin- 

 guished from the body of the hydranth. 6 or 8 medusa-buds, in various stages of develop- 

 ment, are arranged in a circlet situated upon some of the hydranths between the distal base 

 and the circlet of tentacles. The terminal hydranths and those near the free end of the main 

 stem bear no medusae, for these appear to be developed upon the old hydranths. The hydroid 

 of Nemopsis is thus a Bougainvillin, but the medusae arise from the sides of the polypites, 

 not from the stems. 



When set free the medusa is flattened and folded so that the manubrium projects beyond 

 the velar opening. In about an hour, however, it expands and begins to swim. It is then 

 about 0.5 mm. in height, and the bell is globular, being about as broad as high. The manu- 

 brium is short and tubular and without oral tentacles. In some individuals there are 8 ten- 

 tacles, 2 at the base of each radial tube. In others there are but 4 primary tentacles, one 

 upon each tentacle-bulb at the base of the 4 radial tubes. 



As development proceeds the marginal tentacles increase in number, those which are 

 nearest the middle of the basal bulbs being the oldest. The new tentacles appear at the sides 

 near the base of the cone-shaped basal bulb. The 4 oral tentacles develop upon the 4 radial 

 sides of the manubrium, and finally the gonads begin to develop upon the 4 radial-canals 

 adjacent to the sides of the manubrium and finally extend down almost the entire length of 

 the radial-canals. 



According to Hargitt, 1901, about 5 per cent of the medusae of TV. bachei display vari- 

 ations of a numerical nature in the radial-canals, manubrium, gonads, and tentacles. 



Ncmopsis crucifera Haeckel. 



Hipprxrcnr crucijera, FORBES, 1853, Trans. Roy. Soc. Edinburgh, vol. 20, p. 313, plate 10, fig. 5. 

 .\ r ertif}fnn cruriftra, HAECKEL, 1880, Syst. der Medusen, p. 635. 



This species is distinguished from TV. bachcl by its dark-red color and possibly by its 

 more nearly spherical bell. 



Bell oval, 4 mm. wide, 4 mm. high. Each of the 4 marginal tentacle-bulbs bears a median 

 pair of short, stiff, club-shaped tentacles, flanked on either side by 2 to 3 longer filiform ten- 

 tacles. There are thus 6 to 8 tentacles upon each marginal bulb. The stomach is cruciform, 

 and its sides extend half-way down the 4 radial-canals. The oral tentacles are short and branch 

 twice dichotomously. The gonads are as in TV. bachei. Forbes shows the stomach, gonads, 

 and tentacle-bulbs of a darker red color than has been observed in TV. bachei. The tentacular 

 ocelli are black. Found by Forbes and Haeckel at Tobermory and Handa Island, off the 

 west coast of Scotland. 



