In this way the hydroid colony becomes composed of two portions of different function, the nutritive " trophosome," composed of non-sexual polyps, and the reproductive " gonosome," composed of sexual medusaindividuals, which never exercise a nutritive function while attached to the colony.
The coenosarc constitutes a system by which the digestive cavity of any one polyp is put into communication with that of any other individual either of the trophosome or gonosome.
- Trophosome without hydrothecae or gonothecae, with monopodial type of budding.
Trophosome arborescent, with hydranths of Bougainvillea-type; gonosome free medusae or gonophores, the medusae with solid tentacles in tufts (lophonematous).
Trophosome encrusting with hydranths of Bougainvillea-type, polyps differentiated into blastostyles, gastrozoids and dactylozoids; gonosome free medusae or gonophores.
Trophosome, polyps with two whorls of tentacles, the lower filiform, the upper capitate; gonosome, free medusae, with tentacles solid and branched.
Trophosome, polyps with a single whorl of capitate tentacles; gonosome, free medusae, with ten tacles branched, solid.
- Trophosome, polyps with two whorls of tentacles, both filiform.
Corymorphidae (including the medusa-family Hybocodonidae).--, Trophosome solitary polyps, with two whorls of tentacles; gonosome, free medusae or gonophores.
Trophosome, polyp with filiform tentacles in three or four whorls.
Trophosome, polyps with scattered filiform tentacles; gonosome, medusae or gonophores, the medusae with hollow tentacles.
- Trophosome polyps After Haeckel, System der Medusen, by with capitate tentacles, simple or permission of Gustav Fischer.
Trophosome (only known in one genus), polyps with two tentacles forming a creeping colony; gonosome, free medusae with four, six or more radial canals, giving off one or more lateral branches which run to the margin of the umbrella, with the stomach produced into four, six or more lobes, upon which the gonads are developed; the mouth with four lips or with a folded margin; the tentacles simple, arranged evenly round the margin of the umbrella.
Trophosome polyps forming branching colonies of which the stem and main branches are thick and composed of a network of anastomosing coenosarcal tubes covered by a common ectoderm and supported by a thick chitinous perisarc; hydranths similar to those of Coryne; gonosome, sessile gonophores.
- Trophosome only known in one genus (Polycanna), and similar to the preceding; gonosome, free medusae with otocysts and with at least eight radial canals, often a hundred or more, simple or branched.
- Trophosome only known in one genus (Thaumantias), similar to that of the Eucopidae; gonosome, free medusae with otocysts inconspicuous or absent, with usually four, sometimes eight, rarely more than eight, radial canals, simple and unbranched, along which the gonads are developed, with numerous tentacles bearing ocelli and with marginal sense-clubs.
- Trophosome unknown; gonosome, free medusae, with four or six radial canals, bearing the gonads, with numerous tentacles, between which occur sense-clubs, without otocysts.
- Trophosome unknown; gonosome, free medusae of deep form, with radial canals branched in a feathery manner, and After Haeckel, System der Medusen, by permission of Gustav Fischer.
Trophosome as in Eucopidae; gonosome, sessile gonophores.
- Trophosome as in the preceding; gonosome, free medusae or gonophores, the medusae with large open otocysts.
(So far as the characters of the trophosome are concerned, the seven preceding families are scarcely distinguishable, and they form After E.
A section apart, contrasting sharply with the families next to be mentioned, in none of which are free medusae liberated from the colony, so that only the characters of the trophosome need be considered.) 8.
The trophosome consists of a mass of coenosarcal tubes anastomosing in all planes.
The nearest approach to the Stylasteridae is perhaps to be found in Ceratella, with its arborescent trophosome formed of .anastomosing coenosarcal tubes supported by a thick perisarc and covered by a common ectoderm.