﻿OF THE ACALEPHyE OF NORTH AMERICA. *315 



Fig. 9 gives another view of the proboscis, the middle part of which is covered with egsis. 



Fig. 10 represents the same apparatus in its utmost state of contraction, the letters o, a, b, c, (/corresponding to the 

 same letters in Fig. 7, 8, and 9. In this state of utmost contraction, the analogy of the proboscis and central digestive 

 cavity of Hippocrene and other naked-eyed Medusae is very obvious. 



Fig. 11. A profile view, to illustrate chiefly the connection of the vertical tubes, e, e, with the proboscis, o, and the cir- 

 cular tube, k, below, and also the inner vertical and circular muscular bundles, i, i ; g, g, lower partition ; I, /, tentacles ; 

 m, m, eye-specks. 



Fig. 12. A sensitive bulb, to show its connection with the circular tube, the vertical tube, and the tentacle ; a being 

 the circular tube ; b, the vertical extremity of a radiating tube ; c, the sensitive bulb; d, the eye-speck; and e, the base 

 of a tentacle, upon the surface of which the clusters of nettling cells are distinctly seen. 



Fig. 13 gives another view of the sensitive bulb, still more enlarged, and seen somewhat from the side ; a, being the 

 eye-speck ; b, the hollow tentacle, in which granules are seen moving, as in the dilatation of the horizontal circular tube, 

 c, and of the vertical radiating tube, d. 



Fig. 14 gives a front view of the sensitive bulb ; a being the vertical tube ; b, the eye-speck ; and c, the hollow ten- 

 tacle, in which granules are also seen. 



Fig. 15 represents the termination of a tentacle. 



Fig. 16 represents its middle part in a state of contraction, so that the clusters of nettling cells do not appear distinctly. 



Fig. 17. Part of a tentacle elongated to the utmost, when the nettling cells appear as isolated clusters. 



Plate VI. — Tiaropsis diademeta. 



Fig. 1 to 8 represent various views of the whole animal. Fig. 1, 2, 6, 7, 8, are of natural size. Fig. 3, 4, 5, con- 

 siderably enlarged. 



Fig. 1 represents it in its utmost state of lateral expansion. 



Fig. 2. Somewhat contracted round the margin, so as to give it a hemispherical shape, as is also seen in Fig. 3 and 4. 



Fig. 6. Contracted at some distance from the margin. 



Fig. 7. The margin being highly contracted, giving it a more globular form. 



Fig. 8. The contraction is carried so far as to give it an almost quadrangular radiated appearance. 



Fig. 3, 4, 5, show the natural connection of all parts, seen in profile and from above ; the radiating tubes are, however, 

 somewhat differently placed in these three figures ; they agree in Fig. 4 and 5 ; a, a represent the ovaries and spermaries ; 

 b, b, the radiating tubes ; c, c, the large eye-specks ; e, e, the central digestive cavity ; and ;', ;', the fringes of the mouth. 



Fig. 9 shows the connection between the central digestive cavity and the radiating tubes; a being the digestive sac ; 

 b, the fringes of the mouth ; and c, the ovaries hanging around the radiating tubes. 



Fig. 10 represents the mouth from below, the fringes being stretched sideways. 



Fig. 11 represents the same as seen from above, so that the radiating tubes are plainly visible, and upon one ray the 

 ovaries are drawn in their normal connection. 



Fig. 12. The fringes of the mouth seen in profile. 



Fig. 13 shows the connection of the circular chymiferous tube with the row of marginal tentacles, and one large 

 eye-speck. 



Fig. 14 represents the connection of the central digestive cavity with the radiating tubes, the circular tube, and the 

 lower partition, from a young specimen. The number of tentacles between a large eye-speck and a radiating tube, and 

 between two large eye-specks, is much smaller than in adult specimens, as may be seen upon comparison with the cor- 

 responding parts of a larger specimen, Fig. 15. 



Fig. 16. The bases of some marginal tentacles, and a large eye-speck, in their connection with the circular tube and the 

 lower margin of the gelatinous disk. 



Fig. 17. One of the large eye-specks ; a being its cluster of pigment-cells ; b, the inner row of large transparent cells • 

 and r, the outer row of transparent cells. 



Fig. 18 represents the contractile cells of the lower partition. 



