MUSEUM OF COMPARATIVE ZOOLOGY. 259 



The young medusa seen from the aboral pole is shown in Plate I. fig. 8. Six- 

 teen radial stripes (e), whose periphery bounds the central region of the bell, 

 have already appeared, and can be seen faintly showing through the transparent 

 walls of the bell. Their general shape is cuneiform. Situated on the bell 

 margin, and alternating with the bodies last mentioned, are sixteen triangular 

 white spots (if). These triangular spots are the velar lappets (vl), which are 

 now solid and not differentiated into the three serrations which characterize 

 the interocular bell margin of the adult. The ocular lappets (tt) are also 

 found on the bell rim. They seem from the very first to arise independently 

 of the velar lappets. They are arranged in pairs alternating with the velar 

 lappets, and enclosing the otocysts as in the adult. 



In many of the young Cassiopece which were examined, one of the oral arms 

 was much more developed than the others. Is this a remnant of a want of 

 symmetry in growth similar to what exists in the strobila stage of the young 

 Aurelia ? 



Linerges Mercurius, Haeckel. 



Plate II. Figs. 3, 4, 5. Plate III. Figs. 4-8, 11, 13. Plate IV. Figs. 3 - 28. 



Representatives of the genus Linerges* probably L. Mercurius, are among 

 the most abundant Discophores found in the Gulf off the Florida Keys. In 

 the tide eddies near the Tortugas Islands, we passeel through long windrows of 

 these medusae, reaching as far as the eye could follow. Linerges is locally 

 called the " mutton-fish thimble," from its shape and the supposition, without 

 foundation as far as I coulel learn, that they constitute the food of the mutton- 

 fish. The bell is thimble-shaped, with vertical walls ; its height is about half 

 the diameter. The outer surface is covereel with small excrescences or tuber- 

 cles. The walls are thin and flexible. The walls of the apex are more rigid 

 than the vertical, and less capable of ^notion. The bell margin is indented 

 with sixteen deep incisions, from each of which hang alternately tentacles and 

 otocysts. The marginal lobes left by these incisions in the bell rim are com- 

 monly carried folded inward at right angles to the vertical bell walls, resem- 

 bling a discontinuous velum. 



There are eight short tentacles, which hang from alternate incisions in the 

 bell rim, and project but a short distance beyond the bell margin. They are 

 capable of very little motion, and are probably solid. t 



The lower floor or inner wall of the bell is formed of muscular fibres, and is 



* Swartz (Neu. Abh. d. Sehwed. Akad., IX.) described in 17S°, under the name 

 Ifsdiua unguiculata, a similar jelly-fish. 



t Haeckel, op. cit., says they are solid in related genera. The specimens of 



'ges described by Haeckel were alcoholic, which fact is an explanation of the 

 difference in coloration in his drawings and mine. Lincnjcs loses its brown color in 

 preservative fluids. 



