24 EMBEYOLOGTCAL MONOGllAPHS. 



is formcil from a portion of the epiWast, which becomes surrounded by hypoblast The cavity, as that of 

 a ncctocalyx, seems to form liy an at first crescentic-formed dissolution of the epibhist. The vitellus {vt.) 

 passes directly into the polypite. The bell {ncx.} is probably (?) provisional (priioitive uectoualyx). The 

 Iiigmentation {pir/.} is characteristic. 



19. Aijalmopiis (Strphtrnomia, auet.) jnctimi, Fewk. From Jletschuikolf, o/>. cit., PI. XII. fig. 9. 



Euibi-yo in which the pneuniatocyst and embryonic tentacles are well developed. The development of this 

 Pliysophore is exceptional in forming a float, instead of a nectocaly.x, at the very beginning. The youngest 

 larva; becomes covered with a sujierftcial layer — epii)last — which is ciliated, and concentrates at one pole, 

 where it forms a pneumatocyst. The second structure to develop is the tentacle, ami no sign of a nccto- 

 calyx has yet appeared, pncy. Pneumatocy.st, around which is what is left of the unabsorbed vitellus. 

 The ovum has the spongy mass in its center, pi;/. Pigment on the pneumatocyst. ptjt. Polypite, with a 

 terminal mouth {or.). The distal end is pigmented. The prominent a]ipendage to the polypite, the 

 tentacle ((■;«. la.), as well as the knot-like bodies which hang from it, are jirovisional structures. 



20-23. Development of PltiiHnplwrn. From Ha'ckel, Zur Entwickelungsgesehichte der .Si]iliono|ihoren. Einevon 

 der Utrechter Gesellschaft filr liunst uiid Wissenschaft Gekrijnte Preissclirift, PI. I. tigs. 4, 8 ; PI. II. 

 fig. 20 ; PI. III. fig. 24. 



20. ^mhryo oi rivjsoplwra at the close of tlie segmentation of the ovum. cb. Epiblast. rt. Spongy mass of 



vitelline cells. 



21. Older larva, in whicli a primitive hydrophyllium has begun to form at one pole. C P. L. Cliamber in the 



first formed hydrophylUum. ch. Epiblast. hb. Hypoblast, which also cncdoses the cliamlier C. P. L. 

 t(br. The layer between c b. and h b., which forms the gelatinous body of the hydrophyllium. vl. Vitelline, 

 or '■ spongy mass of cells." 



22. An older larva (pjimitive larva), in which a primitive hydrophyllium is fully formed. C. P. %. Chamber of 



the primitive larva, cm. fa. Embryonic tentacle, gm. Buds, the fate of which is not clearly known 

 (probably hydrocysts). Jib. Hypoblast, ms i. Gelatinous layer (inesnbhist ?). P'jt- Polypite. vl nj. 

 Kematocyst. i). Canal leading from the chamber, C. P. L., to the cluster of uematocysts {lUci/.) (Hadial 

 tube of a nectocaly.x '.) The primitive liydrophyllium of this stage is a transitory structure. 



23. Larva, after the loss of the primitive hydropnyllium. Jil.hijcij. Filament of the hydrocyst. hycy. Hydro- 



cyst, ya. Stomach, la. ap. Lateral appendages to the embryonic tentacle, la. Embryonic tentacle. 

 11 ex. First formed nectocalyx. ntcij. Nematocyst. or. Jlouth, not yet open (?). 



24. Praya. From lletschnikoflr, op. cit., PI. YII. fig. IC. 



Embryo in what may be called a Monojyhycs stage, which corresponds with the so-called primitive larva. 

 iicx. Nectocalyx. pyl. Polypite. socy. Somatocyst. itbr. Umbrella. The beluiet-shapcd body (primi- 

 tive hyilrophyllium), probably provisional. 



25. Dlplophysa iiicrmin. From Fewkes, Studies of the Jellyfishes of Xarragausett Day, Iliill. Mns. C'omp. Zoijl., 



Vol. VIII., No. 8; PI. VI. fig. 12. a. ncx. Anterior nectocalyx. yo ph. Gonoiihore 9. <x(. Ovary. 

 socy. Somatocyst. la. Tentacle. 



26. 27. Viphycs Sicholdii. From P. E. Miiller, lagttagelser over nogle Siphonophorer, Nalurh. Tidsskr., 3 K. 7 B., 



PI. \1. fig. 1 ; PI. Xll. fig. 4. 



26. Portion of a stem with two attached members, which later develop separately from each other and from the 



axis. ax. Axis. hyph. Hydrophyllium. pyl. Polypite. A tentacle is also developed, and is shown 

 retracted under the hydrophyllium. 



27. "£«rfo.i'ia form " of one of the last after sejiaration from the axis, yo ph. Gonophore ((J ?). socy. Somato- 



cyst. la. Tentacle, ubr. Umbrella, 



28. Eitdoxin Lessonii. From Fewke.s, o;). Ci7., PI. VI. fig. 8. Fully developed j?i<(feci(i. go 2>h. Gonophore J. 



nc ,r. nectocalyx. oa. Ovary, so cy. Somatocyst. 



The tentacle is cut olf b(dow the third tentacular knob. 



29-31. From Chun, Ueber die Cyclische Entwickelung \ind die Verwandtschaftsverhaltnisse der Siphouophoren. 

 Silzungs. Acad. IFiss. Berlin. No. LIl. p, 1155., PI. -XVII. figs. 1, 2, 4. 

 The successive stages in the cyclical growth of Eadoxia, according to Chun, aie ; I. Monophycs (2'.'). 

 II. Muygla:a (31). III. Eiuhxia (2S). 



29. Monophycs priinordialis. Chun, "First generation." A larva pidbably homologo\is with figs, 17, 24, and 



the young Agalma (PI. VII. fig. 11), which h.as been called the primitive larva, pyl. Polypite. 

 r.lh. Radial tnbe. sucy. Scauatocyst. ubr. Umbridla. 



The anterior nectocaly.x (Muggiuia nectocalyx) may be devehi|nil lioni the small bud .it the basi' ol the 

 polypite. 



