MEM. M. C. Z., IX. No. 3.— ACALEPHS, POLYPS. 17 



11-13. Cunina rhododactyla. From Metsehnikoff, op. cit., PI. V. figs. 1, 2, 7. 



11. Youngest observed "cunina bud," found in tlie gastric cavity. Perlmps developed from an egg. The long 



projection upward, with solid hypobl.istic a.xis, is a tentacle. Tln-re are two layers, and a gastric cavity in 

 th(! body. 



12. The same, still older, with two tentacles and a mouth opening already formed. In stages intermediate 



between this and figure 1-3 there is little change besides the addition of new tentacles and the growth of a 

 " stolon " from the middle of the disk. From this stolon, when there ai'e twelve tentacles, buds develop. 



13. A larva with two buds (,7»t'. and gni^.) on the stolon. The oldest bud ('/m*. ) has two tentacles and an open 



mouth. The second bud has no tentacles. While the fate of these buds is unknown, the original medusa, 

 upon which the budding has ccsased, was observed to develop into a medusa resembling the parent. 



U-17. Cunina oclonaria, McCr. From McCrady, Description of Oceania (Turritopsis) nutricula, nov. spec, 

 ■and the Embryological History of a singular Medusan Larva, found in the cavity of its Bell, PI. VI. 

 figs. 20, 27 ; pi. VII. figs. 32, 33. 



14. Lai-val Cunina, found hanging in the bell cavity of Modceria {Turritopsis) nntricula, McCrady. ga. Stomach 



opening through a long, flexible, tubedike body, through a terujinal mouth [or), ta. Tentacles by which 

 the larva hangs. 



15. A still older larva, in which the umbrella (uhr.) and the otocysts (ocy.) have begun to form. Four tentacles 



have developed from the body in place of the two already formed, gri. Stomach, or. Mouth. 

 10. The young medusa now leaves the bell cavity of its host, and escapes in the form here represented. Seen from 

 below (oral), ga. c. Gastric ehamlier. man. Manubrium, o eg. Otocyst. ta. Tentacle, iibr. Umbrella. 

 This stage may be calle<l the Ephyra stage. 



17. Side view of the last. oq/. Otocyst. ta. Tentacle, ubr. Umbrella. 



18-20. Development of Cunina rhododadyi a. 



18. A stolon taken from its attachment to the tongue of Carmarina haslata, with medusa buds in all conditions 



of grov\th. 



19. From Uljanin, nPOIICXOJIWEHIII 101111111, IIO^KyroilUlXCJI Bl }KE.iy,T,K1; rEPIOHIIJi;t. 



II3t,CTIfl IIMnEPATOPCKArO OBUIECTBA JIOBIITE.IEU ECTECTB03HAHIfl, AHTPOIIO- 

 .TLOrill II 3TII0rPA$III. MOCKBA. 1876. PI. I. fig. 9. A similar but smaller stolon, with many 

 attached medusfe before liberation from attachment, to,'. Points of attachment to the " tongue " of the 

 Carmarina. 



20. From Haickel, op. cit., PI. VI. fig. 76. A bud which has loosened its attachment to the stolon and become 



free (Ephyra stage), ga. Stomach. ?!. Nerve, ocg. Otocyst. or. Jlouth. ta. Tentacle, tb. Tube (?). 

 ubr. Umbrella, vol. Velum. 



21-36. Development of Gcryonia. From Fol, Die erste Entwickelung der Geryoniden eies, Jenaisch. Zeitsch., 

 \o\. VII. Ph XXIV. figs. 1, 2, 3, 5, 6, 7, 11, 12, 13, 15 : PI. XXV. figs. 16, 17, 18, 19, 23, 24. 



21. Fertilized ovum with spermatozoa (.f;!. ) in the mucus envelope. ;)/('. Folds in the egg membrane, m. ISTucleus. 



epl. Epiplasm (upper plasmic layer), hpl. Hypoplasm (lower plasmic layer), vt. )n. Vitelline membrane. 

 X. Mucus covering. 



22. The first plane of segmentation, dividing the ovum into two segmentation spheres, epl. Epiplasm. 



hpl. Hypoplasm. nl. Cell nucleus. /3. Protoplasmic dots arranged in star rays. 



23. Embryo after the formation of a second plane of segmentation, epl. Epiplasm. h pL Hypoplasm. 



nl. Nucleus. }iU. Folds in the membrane of the egg. vc. Vacuoles between the spheres, vt. m. Vitel- 

 line membrane. 



24. Embryo after the formation of the fourth plane of segmentation, consisting of si.xteen cells. A segmentation 



cavity is found within, into which opens a blastopore (bip). nl. Cell nncleus. vi. Kow of vacuoles. 



25. Tlie ovum after the formation of the fifth plane of segmentation, consisting of thirty-two cells. The process 



of cell division, known as delamination, has begun in this embryo. Up. Blastopore, vc. Row of vacuoles. 

 Each of the thirty-two segments is divided into two unequal parts, of which the smaller is formed of gran- 

 ular, and the larger of granular and transparent protoplasm. In the next stage n division of the thirty-two 

 larger cells takes place, and in each of these a line separates the granular fiom the transparent pi'otoplasm. 

 The sixty-four masses of Icnslike sha|ie, composed of granular protoplasm, thus formed, go to make up an 

 outer cpiblastic layer, while the thiily-two masses of transparent protoplasm form the hy|ioblnst. 



26. The ovum after the .sixth plane of segmentation. It consists of thirty-two small cells, external (c ;)0, and 



thirty-two large cells (A;)')- '^- ''''»"• Segmentation cavity. AUi^ady the division of the cells {epl) into 

 a, a', has begun. 



