Ea c h cordylus is a tentacle-like structure with an endodermal axis containing an axial cavity which may be continuous with the ring-canal, or may be partially occluded.
In contrast with the polyp, the longitudinal muscle-system is entirely ectodermal, there being no endodermal muscles in craspedote medusae.
Further, two distinct types of otocyst can be recognized in the Hydro medusae; that of the Leptolinae, in which the entire organ is ectodermal, concrement-cells and all, and the organ is not a tentaculocyst; and that of the Trachylinae, in which the organ is a tentaculocyst, and the concrement-cells are endodermal, derived from the endoderm of the modified tentacle, while the rest of the organ is ectodermal.
Endodermal core (end.), Vogel.
N.c, Nerve-cushion; of the ring-canal, but end, endodermal concrement-cells; con, later becomes separated otolith.
Two kinds of cells - (I) end, Endodermal concrement-cells.
In this case the pigment-cells are endodermal, forming a cup of pigment in which the visual cones are embedded.
C, Cordylus, composed of flattened ectoderm ec covering a large-celled endodermal axis en.
The endodermal spadix (sp) of the sporosac represents the endoderm of the manubrium; the ectodermal lining of the sporosac (ex.) represents the ex-umbral ectoderm of the medusa; and the intervening layers, together with the sub-umbral cavity, have disappeared.
There is, however, no evidence whatever for this, the gonads of Hydra being purely ectodermal structures, while all medusoid gono phores have an endodermal portion.
In addition to tentacles, there may be marginal cirri (Laodice) with a solid endodermal axis, spirally coiled, very contractile, and bearing a terminal battery of nematocysts.
Medusae with sense-organs represented by otocysts derived from modified tentacles (tentaculocysts), containing otoliths of endodermal origin, and innervated from the ex-umbral nerve-ring.
Both these medusae have sense-organs of a peculiar type, which are said to contain an endodermal axis like the sense-organs of Trachylinae, but the fact has recently been called in question for FIG.
Endodermal cell of Phanerogam, with suberized central band on radial and transverse walls.
1, v.), so that the endodermal cells cannot be split apart to admit of the formation of intercellular spaces, and an air-tight sheath is formed round the cylinder.
The mass of the arch-enteron or invaginated endodermal sac has taken on a bilobed form, and its cells are swollen (gs and tge).
When the gonads are endodermal, they are formed on the floor of the stomach; when ectodermal (G, see fig.
(Modified from Horst.) A, Blastula stage (one-cell-layered eaten its way into the in sac), with commencing invaginated endodermal sac, vagination of the wall of the and the cells pushed in with sac at bl, the blastopore.
A second essential difference between Coelentera and other Metazoa (except Parazoa) is that in the former all spaces in the interior of the body are referable to a single cavity of endodermal origin, the "gas*ro-vascular cavity," often termed the coelenteron: the spaces are always originally continuous with one another, and are in almost every case permanently so.
Their ectodermal muscles are mainly longitudinal, their endodermal muscles are circularly arranged on the body-wall.
The medusoids have no true velum; in some cases a structure more or less resembling this organ, termed a velarium, is present, permeated by endodermal canals.
4) a structure is found termed a velarium (Ve), which is a flap hanging down from the margin of the umbrella, and which consists of a fold of the subumbral ectoderm containing endodermal canals.
Endodermal muscles are found in the phacellae, and in such forms as Lucernaria, longitudinal (vertical) muscular tracts or bands are found in the taeniolae, which, according to some authorities, are xxiv.
17 a of endodermal origin, but which, according to recent observations, are formed in the walls of the infundibular cavities, and are therefore of ectodermal origin.
Con, Endodermal concretion continued into the tentacuthe hood.
From the edges of the vase the four primary tentacles grow out, each a slender filament with a solid endodermal axis.
There remains only the third feature, the endodermal gonads, as an argument for uniting the Scyphomedusae with the Anthozoa, against which must be set all the peculiarities of medusan organization in which the Scyphomedusae resemble the Hydromedusae.
The young stems, and the older stems of certain species, are clearly monostelic; but in other species an inner and outer endodermis may be present, or an endodermal layer surrounds each bundle.
The Malpighian tubes of Hexapods are outgrowths of the proctodaeum, but those of Scorpion and the Amphipod Crustacea are part of the metenteron or endodermal gut, though originating near its junction with the proctodaeum.
The segmentation is peculiar, and leads to the formation of a solid gastrula, consisting of a cortex of ectoderm nuclei surrounding a central endodermal mass, which is exposed at one point - the blastopore.