OF THE ACALEPIK^J OF NOUTH AMERICA. 291 



The peculiarity in the tentacles of this genus (Plate VI. Fig. 3, 4, and 5) consists in 

 their regular distribution all round the lower margin of the body, having each a small eye- 

 speck at the base ; but in addition to these, there are eight larger eye-specks (Plate VI. 

 Fig. 3, 4, and 5, c, c), without tentacles, placed in the same row with the tentacles, but some- 

 what lower, and at equal distances from each otiier, being indeed, morphologically speak- 

 ing, of the same kind as the smaller ones, only more individualized as organs of sense, stand- 

 ing out more prominently, and probably performing more decided visual functions, than the 

 little black specks at the base of the tentacles. These eight ocelli, though in reality very 

 small, nevertheless readily strike the attention of the observer from their very deep black 

 color. They are placed (Plate VI. Fig. o) in pairs between the radiating tubes, and rath- 

 er near these tubes, so that the distance between them all is equal, there being none upon 

 the tubes themselves. 



The tentacles around the margin are so short, as to appear like an elegant little 

 fringe all around. But the four radiating tubes are a striking feature in the appearance of 

 these animals, not so much from their dimensions and prominence, as from the fact, that 

 the ovaries or spermaries (Plate VI. Fig. 5, a, «, and Fig. 9, c, c) are attached to the middle 

 of these tubes, in the form of elongated ribbons of a dark color, which bring out the position 

 of the radiating tubes much more distinctly, and almost force the eye to notice the slender 

 tubes (6, b) with which they are connected. Finally, the central proboscis (Plate VI. 

 Fig. 3, 4, and 5, e), with its fringes (?', i), also attracts attention ; and the whole animal 

 may very well be compared to a diminutive umbrella, with four spreading rays, thicker in 

 the middle, a very short handle in the centre, and light, delicate fringes with dark specks 

 around the margin, swimming gently in the water, and moving voluntarily, with much 

 grace, in all directions. 



With regard to all the prominent features of its structure, Tiaropsis stands about interme- 

 diate between Sarsia and Hippocrene, especially in the arrangement of the alimentary sys- 

 tem, and the fringes of the margin in their connection with the eye-specks. The proboscis 

 (Plate VI. Fig. 9, a) is short ; the central cavity is small, but it is not so completely shut up 

 and permanent in its form as in Hip[)ocrene, nor so movable and protractile and retractile 

 as in Sarsia. It may expand (Fig. 12), unfold its fringes (Fig. 9, b), stretch itself in one di- 

 rection or the other, adapt its outline to the bodies upon which it feeds, and display a great 

 range in its movements and in the changes of form and extension which it successively as- 

 sumes, without, in that respect, approximating in any measure to the extraordinary power of 

 expansion and contraction which is so characteristic of the proboscis of Sarsia. If we could 

 imagine the central cavity of Hippocrene (Plate I. Fig. 1) to be exceedingly movable, instead 

 of preserving its fixed quadrangular form, and the lobe of its margin to be regularly undulat- 



