MEM. M. C. Z., IX. No. 3.— ACALEPHS, I'OLITS. 43 



11. More advanced stage of tlif^ 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 he followed by a fourtli. In swinnuiiiy, 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. Tlie two new tentacles are la'., ta". 



14. A seven-tentacle stage, much contracted. The lifth tentacle (3) has reached the length of the four older 



ones. The sixth and seventli havi- hoth appeared in the .same intertentacniar space, namely, the one ad- 

 jacent to the space occupied by the Kfth. The oral lijis show a maxinmni ]irotriision. Two of the clavate 

 organs are pedunculate ; two, attached near the bases of the sixth and seventh tentacles, are still sessile. 

 Note. — The tentacle marked "5" is stated by the author to be the lil'tli, which at this .stage 

 reaches the size of the first four. One would naturally infer that ia'. of fig. 13, being the larger, 

 would be the new tentacle first to attain the size of the other four ; s\ich however cannot he the case, 

 since in fig. 14 the relative j'osition of the fifth as compared with the sixtli 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. Edmardsia (sp.?). 16-22. From Alexander .\gassiz, On Arachnactis brachiolata, a .species of floating 

 Actinia found at Nahant, Massachusetts. Boston Jour. N.at. Hist, Vol. VII., pp. 523-531 and 5 woodcuts; 

 and from drawings by Alexander Agassiz at Nahant, Sept., 1862. 



Note. — The natural attitude of the animal while swimming is witli the tentacles down, the younger 

 tentacles, however, being on the side nearest the surface. 



IG. The yonng larva with oidy four marginal tentacles, seen from the side (dorsal ?) bearing the youngest pair. 

 Tlie two in the distance are the large pair of tentacles at the opposite extremity of the nmuth-slit. The 

 slit and the folds from whicli are formed the labial tentacles are seen edgewise, and there are already indi- 

 cations of the existence of mesenterial filaments. The large polj-gonal "yolk-cells" form a central mass, 

 which slowly revolves, and is reduced in size as the larva increases in age. 



1 7. Oral view of a larva witli three pairs of tentacles, beside the odd tentacle whieli lies in the axis of the oral elonga- 



tion and in this figure is jilaced 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 around the mouth, and project straight up as seen in fig. IG. 



18. A later stage, seen from tire edge (ventral?) whicli 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 ihe 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 ((//). 



20. Much later stage with 13 tentacles, seen fi'om tlu' (dorsal?) edge which bears the youngest tent.acles. 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 sjjhere of yolk- 

 cells is much reduced in proportion to the size of the cavity. 



21. View of the same from the ventral (?) edge, only one-half of the oral end being shown; the large pair of 



oral tentacles quite prominent. 



22. 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 aw.ay from 

 the odd tentacle of the ventral (') margin. 



23. From a drawing of an Edwardsia witli 10 tentacles wdiich 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 unpuljlishcd papi-r liy F.. L. JIark, on the <levelnpment of an Edirardsia 

 parasitic in its earlier stages in Mnemiopsis Leidyi, perhaps Edwardsia lincala Vei-rill. Figui'es 26 and 33 

 were drawn from living specimens toward the end of October 1882, the others, either at Newport, F.. I., in 

 August 1882, or from material collected at that time. 



24. Outline of Mnemiopsis showing numbers of the iiarasites of various sizes grouped about the infundibuluin 



and the beginnings of the radial canals. Many stages, and often in greater numbers, are usually to he 

 found in a single jelly-fish. They are more or less translucent ami 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 Irom the truncate oral end for a litth; distance. The eight mesenteries, 

 which are already formed, are not shown in the <lrawing. 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 C'erianllins 

 larva shown in fig. 10. In this condition it leads a free life. It swims like actinia larvte with the aboral 

 end foremost. 



