26 



corpuscles contained in the marginal capsules in Geryonia pellucida 

 (p. 46.) 



In Cephea Wagneri (Will), a covered-eyed species, the auditory 

 capsule is thus described : " It is about one-sixth of a line in size 

 and placed upon a thick stem, which arises from a transparent yel- 

 lowish mass, placed in the excavation of the more compact bean- 

 shaped substance (described as situated in the nine deeper marginal 

 incisures). The upper border of this substance is deeply excavated 

 on the sides, the lobes extend far into it, and below, a membrane is 

 stretched across. In this way the auditory capsule is entirely covered, 

 and can even be partially retracted. It consists of a delicate mem- 

 brane, crammed full of hexahedral crystals from the one-hundredth to 

 one-eightieth of an inch in diameter. The circulation of fluid seen 

 by Ehrenberg in the stem, is only a part of that produced by ciliary 

 movement in all the aqueous passages ; a motion of the water resem- 

 bling circulation." 



In Polyxenia leucostyla, a naked-eyed Medusa, the marginal bodies 

 are thus described : — " They are placed in the middle, between the 

 marginal tentacles, close upon the marginal vessels. Their number 

 is very inconstant, and does not always correspond with that of the 

 tentacles. They have a slender peduncle (?) by which they are affixed 

 to a yellowish substance lodged in a slight incurvation of the margi- 

 nal vessel, from which, however, it projects pretty considerably. 

 Although the vesicle has a double marginal shadow, still I believe 

 that it consists of only a single membrane. With respect to its con- 

 tents, it differs from all known forms in the circumstance that it 

 contains only a single perfectly spherical corpuscle, almost entirely 

 filling the vesicle, and applied close to the inner wall for two -thirds 

 of the periphery. I was unable to remark any motion in it. It is 

 dissolved by dilute muriatic acid." 



In Cytceis polystyla, a naked-e} r ed species, the so termed auditory 

 capsules are not placed between the tentacles as in the former in- 

 stance, but beneath, or on the inner side of the tentacular bulb, 

 whether there be a tentacle prolonged from it or not. They are not 

 pedunculated, but placed immediately beneath the epidermis, about 

 the one-hundred-and-fiftieth of an inch large. They contain a great 

 number of intensely reddish-yellow roundish corpuscles, with an ir- 

 regular jagged outline. They are soluble with effervescence in 

 muriatic acid. 



In Geryonia pellucida (Will), a naked-eyed species, " The capsules 

 are placed on the marginal vessels in very inconstant number; 



