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MEM. M. C. Z., IX. No. 3.— ACALEPHS, POLYPS. 43 
“11. More advanced stage of the same individual. To the two rudiments of tentacles which made their appear- 
ance 24 hours earlier, is now added a third, which is soon to be followed by a fourth. In swimming, the 
end opposite the tentacles is in advance. 
12. Beside the four tentacles there is a pair of oral elevations. Compare or. ta., fig. 13. 
13. Oral aspect of a six-tentacle stage. The two new tentacles are ta/., da!!. 
14. A seven-tentacle stage, much contracted. The fifth tentacle (5) has reached the length of the four older 
ones. The sixth and seventh have both appeared in the same intertentacular space, namely, the one ad- 
jacent to the space occupied by the fifth. The oral lips show a maximum protrusion. ‘Two of the clavate 
organs are pedunculate ; two, attached near the bases of the sixth and seventh tentacles, are still sessile. 
Norr.—The tentacle marked “5” is stated by the author to be the fifth, which at this stage 
reaches the size of the first four. One would naturally infer that ¢a/. of fig. 13, being the larger, 
would be the new tentacle first to attain the size of the other four; such however cannot be the case, 
since in fig. 14 the relative position of the fifth as compared with the sixth and seventh does not 
admit this conclusion. 
15. Stage —about 30 days older than that of fig. 10 — with seven tentacles of equal length and four peduncu- 
lated club-shaped organs, m nt. fil. 
16-23. Edwardsia (sp.?). 16-22. From Alexander Agassiz, On Arachnactis brachiolata, a species of floating ~ 
Actinia found at Nahant, Massachusetts. Boston Jour. Nat. Hist., Vol. VII., pp. 525-531 and 5 woodcuts; 
and from drawings by Alexander Agassiz at Nahant, Sept., 1862. 
Nore. — The natural attitude of the animal while swimming is with the tentacles down, the younger 
tentacles, however, being on the side nearest the surface. 
16. The young larva with only four marginal tentacles, seen from the side (dorsal?) bearing the youngest pair. 
The two in the distance are the large pair of tentacles at the opposite extremity of the mouth-slit. The 
slit and the folds from which are formed the labial tentacles are seen edgewise, and there are already indi- 
cations of the existence of mesenterial filaments. The large polygonal ‘‘ yolk-cells” form a central mass, 
which slowly revolves, and is reduced in size as the larva increases in age. 
‘17. Oral view of a larva with three pairs of tentacles, beside the odd tentacle which lies in the axis of the oral elonga- 
tion and in this figure is placed below. The disk should have been represented more strongly compressed 
laterally. d@? (dorsum?) The region of the formation of new tentacles. The oral tentacles are as yet sim- 
ple thickenings of the walls avound the mouth, and project straight up as seen in fig. 16. 
18. A later stage, seen from the edge (ventral?) which bears the odd tentacle, and showing the labial tentacles 
directly above the latter. A pair of mesenterial filaments and the sphere of yolk-cells are seen through 
the wall of the body. 
19. Oral aspect of the same stage as that of fig. 18. The odd tentacle (ventral edge?) down. The paired ten- 
tacles decrease in size toward the dorsum (d ?). 
20. Much later stage with 13 tentacles, seen froin the (dorsal?) edge which bears the youngest tentacles. The out- 
line of the oral lips seen through the tentacles ; the odd tentacle in the distance. The mesenteries are 
symmetrically arranged and proportional in size to the corresponding tentacles, and the sphere of yolk- 
cells is much reduced in proportion to the size of the cavity. 
21, View of the same from the ventral (7) edge, only one-half of the oral end being shown; the large pair of 
oral tentacles quite prominent. 
A stage less advanced than the last, seen from the left (?) side, the labial tentacles seen through the margi- 
nal ones. The ‘‘digitate appendages” (mesenterial filaments) have their convexities turned away from 
the odd tentacle of the ventral {’) margin. 
23. From a drawing of an Ldwardsia with 16 tentacles which was raised from ‘‘ Arachnactis” and drawn by 
Alexander Agassiz at Newport, R. I., Sept. 1872. One pair of the mesenterial filaments is much more de- 
veloped than the remaining pairs. Seen from the ventral (?) side. 
24-33. From drawings illustrating an unpublished paper by E. L. Mark, on the development of an Ldwardsia 
parasitic in its earlier stages in Mnemiopsis Leidyi, perhaps Edwardsia lineata Venill. Figures 26 and 33 
were drawn from living specimens toward the end of October 1882, the others, either at Newport, R. I., in 
August 1882, or from material collected at that time. 
24. Outline of Mnemiopsis showing numbers of the parasites of various sizes grouped about the infundibulum 
and the beginnings of the radial canals. Many stages, and often in greater numbers, are usually to be 
found in a single jelly-fish. They are more or less translucent and of a delicate pinkish color. 
25. One of the larger parasitic individuals, removed from the jelly-fish. j. The pharyngeal sac is very short 
and may be seen projecting inward from the truncate oral end for a little distance. The eight mesenteries, 
which are already formed, are not shown in the drawing. On separating from its host, the parasite con- 
tracts, though slowly, to such an extent that its proportions are about the same as those of the Cerianthus 
larva shown in fig. 10. In this condition it leads a free life. Tt swims like actinia larvee with the aboral 
end foremost. 
