24 EMBRYOLOGICAL MONOGRAPHS. 
is formed from a portion of the epiblast, which becomes surrounded by hypoblast. The cavity, as that of 
a nectocalyx, seems to form by an at first crescentic-formed dissolution of the epiblast. The vitellus (vf.) 
passes directly into the polypite. The bell (new.) is probably (?) provisional (primitive nectocalyx). The 
pigmentation ( pig.) is characteristic. 
19. Agalmopsis (Stephanomia, auct.) pictum, Fewk. From Metschnikoff, op. ctt., Pl. XII. fig. 9. 
Embryo in which the pneumatocyst and embryonic tentacles are well developed. The development of this 
Physophore is exceptional in forming a float, instead of a nectocalyx, at the very beginning. The youngest 
larve becomes covered with a superficial layer — epiblast — which is ciliated, and concentrates at one pole, 
where it forms a pneumatocyst. The second structure to develop is the tentacle, and no sign of a necto- 
calyx has yet appeared. prey. Pneumatocyst, around which is what is left of the unabsorbed vitellus. 
The ovum has the spongy mass in its center. pig. Pigment on the pneumatocyst. pyt. Polypite, with a 
terminal mouth (or.). The distal end is pigmented. The prominent appendage to the polypite, the 
tentacle (cm. tw.), as well as the knot-like bodies which hang from it, are provisional structures. 
20-23. Development of Physophora. From Heckel, Zur Entwickelungsgeschichte der Siphonophoren. Eine yon 
der Utrechter Gesellschaft fiir Kunst und Wissenschaft Gekronte Preisschvift, Pl. I. figs. 4, 8; Pl. II. 
fig. 20; Pl. III. fig. 24. 
20. Embryo of Physophora at the close of the segmentation of the ovum. ¢b. Epiblast. 2t- Spongy mass of 
vitelline cells. 
21. Older larva, in which a primitive hydrophyllium has begun to form at one pole. @. P. Z. Chamber in the 
first formed hydrophyllium. ¢b. Epiblast. 5. Hypoblast, which also encloses the chamber C. P. L. 
ubr. The layer between ¢b. and i b., which forms the gelatinous body of the hydrophyllium. 7. Vitelline, 
or ‘* spongy mass of cells.” 
22. An older larva (primitive larva), in which a primitive hydrophyllium is fully formed. ©. P. L. Chamber of 
the primitive larva. em. fa. Embryonic tentacle. gm. Buds, the fate of which is not clearly known 
(probably hydroeysts). 6. Hypoblast. ms. Gelatinous layer (mesoblast ?). pyt. Polypite. nt cy. 
Nematocyst. 7. Canal leading from the chamber, C. P. L., to the cluster of nematoeysts (2 cy.) (Radial 
tube of a nectocalyx ?) The primitive hydrophyllium of this stage is a transitory structure. 
93. Larva, after the loss of the primitive hydropnyllium. il. hy cy. Filament of the hydrocyst. hy cy. Hydro- 
eyst. ga. Stomach. Ja. ap. Lateral appendages to the embryonic tentacle. ta. Embryonic tentacle. 
n cx. First formed nectocalyx. at cy. Nematocyst. or. Mouth, not yet open (7). 
24. Praya. From Metschnikoff, op. cit., Pl. VII. fig. 16. 
Embryo in what may be ealled a Monophyes stage, which corresponds with the so-called primitive larva. 
nex. Nectocalyx. pyt. Polypite. socy. Somatocyst. “ubr. Umbrella. The belmet-shaped body (primi- 
tive hydrophyllium), probably provisional. 
25. Diplophysa incrmis. Yrom Fewkes, Studies of the Jellyfishes of Narragansett Bay, Bull. Mus. Comp. Zodl., 
Vol. VIIL, No. 8; Pl. VI. fiz. 12. a. aex. Anterior nectocalyx. go ph. Gonophore Q. oa. Ovary. 
socy. Somatocyst. ta. Tentacle. 
26, 27. Diphycs Sieboldit. From P. E. Miiller, Iagttagelser over nogle Siphonophorer, Naturh. Tidsskr., 3 R.7 B., 
Pl. XI. fig. 1; Pl. XID. fig4. 
26. Portion of a stem with two attached members, which later develop separately from each other and from the 
axis. az. Axis. hyph. Hydrophyllium. pyf. Polypite. A tentacle is also developed, and is shown 
retracted under the hydrophyllium. 
97. ‘‘Eudoxia form” of one of the last after separation from the axis. go ph. Gonophore (g%). so cy. Somato- 
cyst. ta. Tentacle. whr. Umbrella. 
28. Eudoxia Lessonii. From Fewkes, op. cit., Pl. VI. fig. 8. Fully developed Eudoxia. go ph. Gonophore @. 
nev. nectocalyx. oa. Ovary. socy. Somatocyst. 
The tentacle is eut off below the third tentacular knob. 
29-31. From Chun, Ueber die Cyclische Entwickelung und die Verwandtschaftsverhaltnisse der Siphonophoren. 
Sitzungs. Acad. Wiss. Berlin. No. LU. p, 1155., Pl. XVII. figs. 1, 2, 4. 
The successive stages in the cyclical growth of Ludoxia, according to Chun, are : I. Afonophyes (29). 
Il. Muggiea (31). Il. Eudoxia (28 
29. Monophycs primordialis, Chun, ‘First generation.” A larva probably homologous with figs. 17, 24, and 
the young Agalme (Pl. VII. fig. 11), which has been called the primitive larva. pyt. Polypite. 
r. th. Radial tube. so cy. Somatocyst. whr. Umbrella. 
The anterior nectocalyx (Afuggiwa nectocalyx) may be developed from the small bud at the base of the 
polypite. 
