"One of the Acalephae; a name given to a large number of marine animals; and redpresenyted chiefly by medusidae."-Whitney, 1902

Acaleph

"One of the Acalephae; a name given to a large number of marine animals; and redpresenyted chiefly by…

"The under surface, showing the mouth in the center, surrounded by the tentacula, and overial chambers exterior to the origins of these." — Chambers' Encyclopedia, 1875

Acalephae

"The under surface, showing the mouth in the center, surrounded by the tentacula, and overial chambers…

"Side-view, showing the tentacula hanging down in their natural position." — Chambers' Encyclopedia, 1875

Acalephae

"Side-view, showing the tentacula hanging down in their natural position." — Chambers' Encyclopedia,…

"Gonoblastidium of Athorybia rosacea, bearing three hydroclysts, a, a gynophore, b, and two androphores, c." -Whitney, 1911

Athorybia Gonoblastidium

"Gonoblastidium of Athorybia rosacea, bearing three hydroclysts, a, a gynophore, b, and two androphores,…

"B, male gonophore of Athorybia rosacea." -Whitney, 1911

Athorybia Gonophore

"B, male gonophore of Athorybia rosacea." -Whitney, 1911

"A, female gonophores of Athorybia rosacea on their common stem or gynophore: a, ovum; b, radial canals." -Whitney, 1911

Athorybia Gonophores

"A, female gonophores of Athorybia rosacea on their common stem or gynophore: a, ovum; b, radial canals."…

"C, female gonophores: a, genital vesicle; b, vitellus; c, radial canals." -Whitney, 1911

Athorybia Gonophores

"C, female gonophores: a, genital vesicle; b, vitellus; c, radial canals." -Whitney, 1911

"D, female gonophores, enlarged: c, radial canals; d, canal of manubrial cavity." -Whitney, 1911

Athorybia Gonophores

"D, female gonophores, enlarged: c, radial canals; d, canal of manubrial cavity." -Whitney, 1911

Auditory and equilibrative organs of jellyfishes. A, of Cunarcha. B, of Pectis. C, of Rhopalonema. D, of Cumarina. Labels: Ok, auditory tentacle; Ol, Otolith; Oh, auditory hairs; n, nerves.

Auditory Organs of the Jellyfish

Auditory and equilibrative organs of jellyfishes. A, of Cunarcha. B, of Pectis. C, of Rhopalonema. D,…

"One of the commonest species, and must have been observed by those who frequent the sea-shore. In the water the creature swims along most gracefully by the contractoin and dilatation of its transparent disk." — Goodrich, 1859

Medusa, aurita

"One of the commonest species, and must have been observed by those who frequent the sea-shore. In the…

"a, tentacula; b, mouth; c, termination of intestine." — Chambers' Encyclopedia, 1875

Beroe

"a, tentacula; b, mouth; c, termination of intestine." — Chambers' Encyclopedia, 1875

"Which is without a central peduncle, yet has numerous long appendages hanging from its border." — Goodrich, 1859

Cuvieria carisochroma

"Which is without a central peduncle, yet has numerous long appendages hanging from its border." —…

Fire corals are colonial marine organisms that look rather like real coral. However they are technically not corals; they are actually more closely related to jellyfish and other stinging anemones. They are members of the phylum Cnidaria, class Hydrozoa, order Capitata, family Milleporidae.

Fire Coral

Fire corals are colonial marine organisms that look rather like real coral. However they are technically…

"The <em>Rhisostoma Cuvieri</em>, a British species, measures two feet, or ever more, in diameter, while some fo the inhabitants of tropical seas are said to attain a still larger size. In calm weather they often swim close to the surface of the sea, in such multitudes as to impede the motion of a boat through the water. Such a fleet as this, seen with the sun shining strongly upon them, is a magnificent specacle, from the beautiful iridescemce with which the sunlight is reflected to the eye of the beholder. With the approach of night this scene of beauty only gives place to another, for these Medusae are exceedingly luminous in the dark." &mdash; Goodrich, 1859

Rhizostoma cuvieri

"The Rhisostoma Cuvieri, a British species, measures two feet, or ever more, in diameter, while…

Eucope diaphana is a species of marine animal in the order Anthomedusae.

Eucope

Eucope diaphana is a species of marine animal in the order Anthomedusae.

Eudendrium cochleatum is a hydrozoan marine animal in the Eudendriidae family.

Eudendrium

Eudendrium cochleatum is a hydrozoan marine animal in the Eudendriidae family.

The simple eye of a jellyfish

Eye

The simple eye of a jellyfish

Hydra are in the Jellyfish family, class Hydrozoa.

Hydra

Hydra are in the Jellyfish family, class Hydrozoa.

Hydra are in the Jellyfish family, class Hydrozoa. Cross-section of the body showing the two layers of cells of the body wall.

Hydra

Hydra are in the Jellyfish family, class Hydrozoa. Cross-section of the body showing the two layers…

If undisturbed, the body and tentacles may occasionally sway gently. If disturbed, a hydra usually shortens until it is a tiny ball.

Hydra

If undisturbed, the body and tentacles may occasionally sway gently. If disturbed, a hydra usually shortens…

Longitudinal section of a hydra.

Hydra

Longitudinal section of a hydra.

Cross section of a hydra.

Hydra

Cross section of a hydra.

Stinging cells of hydra, highly magnified. Cell containing thread capsule.

Hydra

Stinging cells of hydra, highly magnified. Cell containing thread capsule.

Stinging cells of hydra, highly magnified. Thread capsule partly discharged.

Hydra

Stinging cells of hydra, highly magnified. Thread capsule partly discharged.

Stinging cells of hydra, highly magnified. Thread capsule fully discharged.

Hydra

Stinging cells of hydra, highly magnified. Thread capsule fully discharged.

"The <em>Hydra Viridis</em> is another freshwater polyp, common to ponds and still waters Sometimes the green hydra inhabits brooks filled with herbage." This image shows the Hydra bearing an embryo ready to detach itself.

Hydra Viridis

"The Hydra Viridis is another freshwater polyp, common to ponds and still waters Sometimes…

"The <em>Hydra Vulgaris</em> inhabits stagnant ponds and slow running waters."

Hydra Vulgaris

"The Hydra Vulgaris inhabits stagnant ponds and slow running waters."

Colonial, plant-like animals closely related to jellyfish, with stinging cells, Any member of the invertebrate order Hydroida (class Hydrozoa, phylum Cnidaria). Hydroids have three basic life-cycle stages: (1) a tiny free-swimming planula larva about 1 mm (0.04 inch) long, which settles and grows into (2) a sessile (attached), usually colonial hydroid stage, which in turn liberates (3) medusa.

Medusa of a Hydroid

Colonial, plant-like animals closely related to jellyfish, with stinging cells, Any member of the invertebrate…

Hydrozoa (hydrozoans) are a taxonomic class of very small, predatory animals which can be solitary or colonial and which mostly live in saltwater. A few genera within this class live in freshwater. Hydrozoans are related to jellyfish and corals and belong to the phylum Cnidaria.

Hydrozoa Encrusting a Small Shell

Hydrozoa (hydrozoans) are a taxonomic class of very small, predatory animals which can be solitary or…

A free-swimming jellyfish of the Class Scyphozoa.

Jellyfish

A free-swimming jellyfish of the Class Scyphozoa.

Jellyfish are saucer-shaped and can be a foot or more in diameter. They are gelatinous and semitransparent.

Jellyfish

Jellyfish are saucer-shaped and can be a foot or more in diameter. They are gelatinous and semitransparent.

Jellyfish are generally of the hydrozoa family.

Jellyfish

Jellyfish are generally of the hydrozoa family.

"Development of young jellyfish. The top one is ready to break away." &mdash;Davison, 1906

Jellyfish

"Development of young jellyfish. The top one is ready to break away." —Davison, 1906

An illustration of a small jellyfish. Jellyfish are free-swimming members of the phylum Cnidaria. ellyfish don't have specialized digestive, osmoregulatory, central nervous, respiratory, or circulatory systems. They digest using the gastrodermal lining of the gastrovascular cavity, where nutrients are absorbed. They do not need a respiratory system since their skin is thin enough that the body is oxygenated by diffusion. They have limited control over movement and mostly free-float, but can use the hydrostatic skeleton of the water pouch to accomplish vertical movement through pulsations of the disc-like body.

Jellyfish

An illustration of a small jellyfish. Jellyfish are free-swimming members of the phylum Cnidaria. ellyfish…

Gonionemus is a type of hydrozoan related to jellyfish. It uses adhesive discs near the middle of each tentacle to attach to eelgrass, sea lettuce or various types of algae instead of swimming. They are small bell shaped and hard to see when hanging on to swaying seaweed.

Gonionemus Jellyfish

Gonionemus is a type of hydrozoan related to jellyfish. It uses adhesive discs near the middle of each…

Gonionemus is a type of hydrozoan related to jellyfish. It uses adhesive discs near the middle of each tentacle to attach to eelgrass, sea lettuce or various types of algae instead of swimming. They are small bell shaped and hard to see when hanging on to swaying seaweed. Enlarged portions of a hydroid colony bearing the mouth and tentalces of this jellyfish are shown here.

Gonionemus Jellyfish

Gonionemus is a type of hydrozoan related to jellyfish. It uses adhesive discs near the middle of each…

Gonionemus is a type of hydrozoan related to jellyfish. It uses adhesive discs near the middle of each tentacle to attach to eelgrass, sea lettuce or various types of algae instead of swimming. They are small bell shaped and hard to see when hanging on to swaying seaweed. Enlarged portions of a hydroid colony bearing the mouth and tentalces of this jellyfish are shown here.

Gonionemus Jellyfish

Gonionemus is a type of hydrozoan related to jellyfish. It uses adhesive discs near the middle of each…

Gonionemus is a type of hydrozoan related to jellyfish. It uses adhesive discs near the middle of each tentacle to attach to eelgrass, sea lettuce or various types of algae instead of swimming. They are small bell shaped and hard to see when hanging on to swaying seaweed. This jellyfish diagram illustrates its method of locomotion.

Gonionemus Jellyfish

Gonionemus is a type of hydrozoan related to jellyfish. It uses adhesive discs near the middle of each…

Fresh water Hydra, a jellyfish, is a many celled animal. Shown enlarged 25 times, is the entire animal.

Hydra Jellyfish

Fresh water Hydra, a jellyfish, is a many celled animal. Shown enlarged 25 times, is the entire animal.

Fresh water Hydra, a jellyfish, is a many celled animal. Shown is a Hydra nettle cells.

Hydra Jellyfish

Fresh water Hydra, a jellyfish, is a many celled animal. Shown is a Hydra nettle cells.

Fresh water Hydra, a jellyfish, is a many celled animal. The organs of defence, nettle cells or lasso cells , in the event of disturbance, the sac will discharge coiled thread an barbs into the body of the intruder.

Hydra Jellyfish

Fresh water Hydra, a jellyfish, is a many celled animal. The organs of defence, nettle cells or lasso…

Fresh water Hydra, a jellyfish, is a many celled animal. The organs of defence, nettle cells or lasso cells , in the event of disturbance, the sac will discharge coiled thread an barbs into the body of the intruder.

Hydra Jellyfish

Fresh water Hydra, a jellyfish, is a many celled animal. The organs of defence, nettle cells or lasso…

Hydroids, related to the jellyfish, have three basic life-cycle stages: a tiny free-swimming planula larva, which settles and grows into a sessile attached, usually colonial hydroid stage, which in turn liberates medusae. An enlarged portion of a hydroid colony (Hydractinia) showing the nutritive polyp (a), the defensive polyp (b), and the reproductive polyp.

Hydroid Jellyfish

Hydroids, related to the jellyfish, have three basic life-cycle stages: a tiny free-swimming planula…

Jellyfish have several different morphologies that represent several different cnidarian classes including the Scyphozoa. Stages in the development of a scyphozoan jellfish shows the attached young.

Scyphozoan Jellyfish

Jellyfish have several different morphologies that represent several different cnidarian classes including…

Jellyfish have several different morphologies that represent several different cnidarian classes including the Scyphozoa. Stages in the development of a scyphozoan jellfish shows the attached young, whin has separated into a number of disks, each of which becomes a jellyfish.

Scyphozoan Jellyfish

Jellyfish have several different morphologies that represent several different cnidarian classes including…

Jellyfish have several different morphologies that represent several different cnidarian classes including the Scyphozoa. Fully developed scyphozoan jellyfish.

Scyphozoan Jellyfish

Jellyfish have several different morphologies that represent several different cnidarian classes including…

"With four foliaceous arms, and long filaments depending from the rim of th umbrella, also found in the South Seas." &mdash; Goodrich, 1859

Pelagia labiche

"With four foliaceous arms, and long filaments depending from the rim of th umbrella, also found in…

Portuguese Man of War floating above the surface of the water.

Portuguese Man of War

Portuguese Man of War floating above the surface of the water.

The Portugures man-of-war has a bladderlike float, and locomotion depends upon the wind and current. they have well-developed stinging cells.

Portuguese Man-of-War

The Portugures man-of-war has a bladderlike float, and locomotion depends upon the wind and current.…

"They usually inhabit the deep seas. They are rarely solitary, but seem to wander about in considerable battalions in the latitudes to which they belong."

Fleet of Medusa

"They usually inhabit the deep seas. They are rarely solitary, but seem to wander about in considerable…

"With a nearly hemispherical body, showing a long proboscis, at the root of which are eight branchiferous appendages, inhabiting the South Seas." &mdash; Goodrich, 1859

Favonia octonema

"With a nearly hemispherical body, showing a long proboscis, at the root of which are eight branchiferous…

"Physalia has no proper mouth, but the food is conveyed to the digestive cavity through a number of flask like appendages, which hang down beneath, each having an orifice and a sort of sucker." &mdash; Chambers' Encyclopedia, 1875

Physalia

"Physalia has no proper mouth, but the food is conveyed to the digestive cavity through a number of…

Obelia, a simple polyp, vertical section, highly magnified, m = mouth opening, as.s = alimentary sac

Polyp

Obelia, a simple polyp, vertical section, highly magnified, m = mouth opening, as.s = alimentary sac

"Fresh-water polype (hydra), two specimens, the one expanded the other contracted, showing multiplication by buddin. bd1 bd2 bd3, buds in various stages of growth." -Parker, 1900

Freshwater Polyp

"Fresh-water polype (hydra), two specimens, the one expanded the other contracted, showing multiplication…

"The <em>Porpitae</em> consist of colonies of floating animals furnished with a cartilaginous, horizontal and rounded skeleton, but they are destitute of crest or veil."

Porpita Pacifica

"The Porpitae consist of colonies of floating animals furnished with a cartilaginous, horizontal…

"These fragile creatures are able to make long voyages on the surface of the sea. Their nature is such that they are required to keep constantly moving in order to sustain themselves in the fluid which they inhabit. There is a double movement of their light skeletons, which may be compared to the action of respiration in the human hest."

Rhyzostoma Cuvierii

"These fragile creatures are able to make long voyages on the surface of the sea. Their nature is such…

A type of comb jelly having two tenticals and no oral lobes.

Saccatae

A type of comb jelly having two tenticals and no oral lobes.

There is a large oblong crested float which buoys the fish up, from which hang many tenticles, which can attain a length of 12 feet. The tenticles produce a powerful stinging sensation when touched.

Portuguese Man of War

There is a large oblong crested float which buoys the fish up, from which hang many tenticles, which…