ba f 
10. 
11. 
13. 
14. 
16. 
17. 
MEM. M. ©. Z., IX. No. 3.—ACALEPHS, POLYPS. 27 
3-5. Agalma elegans, Fewkes. From sketches by Fewkes. 
Larva older than the last, with the polar cap more raised and a central chamber (C. P. L.). The layer eb. 
was not observed to be differentiated into two or more divisions, although it may have component parts 
corresponding to the epiblast, hypoblast, or even an intermediate gelatinous layer (mesoblast). Nuclei (?) 
were observed in the vitelline cells. 
Older larva, with the chamber (C. P. Z.) surrounded by two layers. ¢b. Epiblast. fb. Hypoblast. 
. Side view of the last. The chamber (C. P. Z.) of the primitive elevation, which is the primitive hydro- 
phyllium, has become tube-like. c/. Vitelline cells (?). nl. Nucleus (2). pig. Pigment patches, with 
rough projections on the surface of the ovum. 
6, 7. Agalma Sarsti. From Metschnikoff, op. cit., Pl. VIII. figs. 6, 7. 
. Larva, showing the first formation of the pneumatocyst, which first appears as an epiblastie structure (¢ b/.). 
eb. Epiblast. ms, Gelatinous thickening, forming the body of the primitive hydrophyllium, and des- 
tined later to increase to a very large size, when the epiblastic layer becomes a thin superticial layer of cells 
stretched over it. § Recess above the spongy mass of vitelline cells. 
. Primitive larva. A common larval condition of the Siphonophora, which many genera of Physophore and 
Calycophore pass through, distinguished on account of a provisional hydrophyllium (or nectocalyx), cover- 
ing as a helmet the vitellus, which may or may not pass directly into a polypite. The chamber C. P. L. 
is lined with hypoblast (5.). The epiblast (¢ 6.) is stfetched over the vitellus, and extends as a very thin 
layer over the primitive hydrophyllium. The great size of the hydrophyllium is caused by the growth of 
the middle or gelatinous layer. pn cy. Pneumatocyst. § Recess between the vitelline cells and the 
hydrophyllium. 
8-10. Agalma elegans. From sketches by A. Agassiz. 
- Larva a little older than the last. C. P. £, Chamber of the hydvophyllium. pr. hy ph. Primitive hydro- 
phylliium. pn cy. Pneumatocyst. 
Still older larva. C. P. Z. Chamber of the primitive bydrophyllium. pr. hyph. Primitive hydvophyllium. 
vt. Vitellus. Of the three buds shown in the figure, the larger is the pneumatocyst, and the two smaller 
(lateral) the rudiments of the serrated hydrophyllia, which later assume great size. vf. Vitellus. 
Older larva, with the primitive hydrophyllium (pr. hy ph.) bent over so as to hide the cavity (C. P. Z.), and 
expose in profile the polypite and serrated hydrophyllium. By this movement the pneumatocyst (pn cy.) 
is brought to the middle of the figure, while at its left are several buds, which later develop into hydro- 
phyllia. 
Agalma Sarsit. From Metschnikoff, op. cit., Pl. VIII. fig. 11. 
Profile view of a larva, in which the margin of the provisional hydrophyllium has grown downward, covering 
the vitellus, from which, however, it is free at the edges. The epiblast (e0.) appears at a projection, gen- 
erally more or less pigmented, which is beginning to push out at the side of the ovum. The hypoblast 
(i. b.) is also visible at the same point, and also lines the chamber C. P. Z. ‘The vitelline cells are some- 
what reduced in number. There are two regions of crimson pigment (pig.). The serrated hydrophyllia 
(ser. hy ph.) are conspicuous by reason, in part, of the large nematocysts in their walls. 
12-17. Agalmea elegans. From sketches by A. Agassiz. 
- Larya of about the same age, and represented in the same position as fig. 10, showing the serrated hydro- 
phyllia (ser. hy ph.) in profile. pn ey. Pneumatoecyst. vt. Vitellus. 
Larva, showing the relation of the primitive hydrophyllium (pr. hy ph.) and the pneumatocyst (pn cy.) 
vt. Vitellus. 
Primitive larva, seen in profile with the spongy mass of cells (vt.) hugging closely the inner wall of the 
epiblast. They here occupy a position similar to the same cells in ZEpibulia (Pl. VI. fig. 13 10). 
pnph. Pneumatophore. pap. Small tubercles, not figured in other figures, and doubtfully called papilla. 
ser. hyph. Servated hydrophyllia in profile. C. P. Z. Chamber of the primitive hydrophyllium now 
reduced to a tube. v¢. Vitellus. 
. Larva of the same age as the last, seen in a plane at right angles, laterally, and from below, indicating the 
position of the large cells in the vitellus (v/.). or. Mouth. pn cy. Pneumatocyst. ser. hy ph. Serrated 
hydrophy!lia. 
Older larva, in which the size of the serrated hydrophyllia (ser. hy ph.) has greatly increased, and a terminal 
cluster of nematocysts has appeared at the distal extremity of a tube situated medially in the hydro. 
phyllium. prey. Pneumatocyst. C. P. Z. End of the cavity of the hydrophyllium. 
Larya older than the last, in which the primitive hydvophyllium has disappeared, and the polypite has 
become very much elongated. A single serrated hydrophyllium (ser. hy ph.) is sketched on one side to 
show its relations to the pneumatocyst (pucy.). Of the small buds below it, the lowest — that with four 
black spots — is probably a tentacle, and the others are immature hydrophyllia. 
