L. auricula. This little iridescent jellyfish, which measures about one and a half inches in diameter, is commonly found attached to eel-grass by a stalk-like projection of the top of the umbrella. Short, globe-tipped tentacles are arranged in eight clusters, each cluster on a raised prolongation of the margin of the umbrella, and in the center of each space between them is a dark kidney-shaped organ called the anchor. These anchors are used for holding, either for suspension or when moving from place to place. The mouth forms a slight quadrangular projection in the center of the bell-like expansion. The arm-like projections are mottled with two rows of spots, which are the ova. Although a free form and capable of moving about, Lucernaria is sedentary in habit. It is sometimes found free, but generally attached by its extremity to eel-grass or Fucus, seldom to rocks. It is constantly changing its shape. The one it most frequently assumes is that of a cup or inverted bell. It is found on the New England coast. (Plate XLIV.)
Genus Pericolpa
P. quadrigata. Umbrella conical and divided by a horizontal constriction into two parts, the lower one being again divided into lobes. There are four long tentacles and four tentaculocysts. It is not found on the coasts of the United States. [pg137]
Genus Charybdæa
C. marsupialis. Umbrella square, flattened on top, and of firm consistency. Four tentacles fall from lobes on the umbrella, and four club-shaped eyes are in marginal notches. Plate-like egg-sacs follow each side of the four radial canals. The bell is one inch in diameter and about two inches in height. It is not found on the coasts of the United States.
Genus Aurelia
A. flavidula. Size eight to ten inches in diameter; disk gelatinous, transparent bluish-white, broad and comparatively flat, with a fringe of short tentacles of even length around the margin; margin broken by eight notches, in each one of which is a club-like organ (tentaculocyst) containing calcareous spots or eyes, which are hidden by lappets or hood-like coverings; groups of nerve-cells also lie in the marginal notches; radial canals branched; manubrium very short, with square mouth, which is surrounded by delicate membranes, or oral arms, each arm being a folded membrane tapering to a point. The edges of the membranes are covered with lasso- or stinging-cells. Four egg-sacs, or gonads, are conspicuous in horseshoe shape around the center of the disk. The gonads are pink in the males, and yellow in the females. These medusæ swim in shoals, and are common everywhere in summer. They may be said to be annual animals, for they make their appearance regularly as free-swimming medusæ in the latter part of April, when they may be seen in immense numbers near the surface when the water is smooth and the sky clear. At this time they are about an inch in diameter. They grow rapidly, and by the end of June have attained their full size. At [pg138] the end of July they are fully developed, and begin to discharge their eggs, which go into the folds around the mouth and remain there until they attain the planula stage. After the spawning period the medusæ, reduced in strength, are unable to resist the storms of the autumn, and many of them are cast ashore; many others, in a more or less wasted condition, float near the surface, but the body is less transparent, its tissues are thickened, its tentacles gone, and general dissolution has commenced. In this condition the medusæ are frequently capsized by the air which accumulates in the empty egg-cavities, and, floating helplessly on the surface, are attacked and destroyed by swarms of small crustaceans; thus their cycle of life is terminated. It has been suggested that the destruction of the mothers, by being cast upon the beaches in the autumnal gales, is a provision to set free the planulæ in a position favorable to their existence; for when liberated they fasten upon the rocks and seaweeds of the shore, where, during the winter months, they develop into strobilæ, which in turn free their saucer-like disks early in April.
Genus Cyanea
C. arctica, the sun-jelly or sea-blubber. This is the largest jellyfish known. Some individuals measure seven and a half feet across the disk and have tentacles more than one hundred feet long. Usually they are three to five feet in diameter, with tentacles thirty to forty feet long. The disk is red, the margin white and scalloped. The tentacles, of different colors, are covered with lasso- or stinging-cells, and are arranged in eight distinct, thick clusters on the margin. From the mouth hang four long and very broad, thin curtains, much folded and ruffled, whose edges at times look as if they were embroidered, because great numbers of discharged eggs are attached to them. Four egg-sacs hang from the disk near the manubrium, and eight sense-organs (tentaculocysts), in hardened coverings, lie in some of the deep incisions of the margin. Cyanea [pg139] is usually solitary, seldom being seen in company with others. It is common on the New England coast, and is frequently found stranded on the beach, where it in no way suggests the beautiful appearance it presents when floating in the water. Like Aurelia, Cyanea has a strobila stage. It is supposed that the young remain near the bottom, for they are seldom seen, while adults are plentiful. They begin to appear in numbers at the end of summer from Cape Cod northward.
C. fulva. This species is found in midsummer south of Cape Cod and is common in Long Island Sound. Its general color is light yellowish-brown, the flowing curtains being the darkest part of the animal. It is not as large as C. arctica, and the lobes of the margin are deeper and more rounded.
C. versicolor. The whole disk is bluish milky-white, the flowing curtains are light brown, and the tentacles are pink. It is not so large as C. arctica. Found in the spring on the southern coast.
Genus Linerges
L. mercurius, the thimble-fish. The English name indicates the form as well as the size of this little brownish jellyfish, which is found near the Florida Keys, extending in lines for considerable distances.
Genus Pelagia
P. cyanella. Umbrella spherical, margin scalloped, tentacles eight in number; four long appendages ruffled on the edges hang from the mouth; size about two inches in diameter; appendages four inches long; color pink. (See next page.)
The Rhizostomæ, or root-mouth jellyfishes, are very remarkable. They have no tentacles, but covering the end of the manubrium and hanging from it like tentacles are oval appendages with numerous minute funnel-like apertures, called suctorial mouths. As the manner of locomotion of jellyfishes is peculiar to themselves, so also is this many-mouthed development unique in the animal kingdom. The type of this group, described below, is found on the Florida Keys. The different species vary in diameter from three to eight inches. [pg140]
Genus Cassiopeia
C. frondosa. This species has a circular disk, on the margin of which are sixteen sense-organs (tentaculocysts), but no tentacles. The lower end of the manubrium, which in other jellyfishes is an open mouth, is closed by eight arms which emanate from it and are usually extended laterally, lying parallel to the disk. These arms are much branched, and the branches, in turn, have numerous appendages. Some of these appendages look like little polyps and have mouths surrounded by crowns of tentacles; others are ovoid bodies without external openings, but with a central cavity connected with vessels leading to the arms. The former are mouths, but the function of the ovoid bodies is not known. Although able to swim freely, Cassiopeia lies usually on its back, as if attached, and languidly opens and closes its disk, rarely changing its position. Its arms, extending upward, appear like the fronds of algæ. These jellyfishes are common on the Florida coast, huddled together on the sands of the coral reefs. (Plate XLIV.) [pg141]
The animals of this class are divided into two subclasses, based on the following anatomical differences: In the first subdivision, which includes the sea-anemones and the reef-building corals, the polyps have numerous simple, hollow tentacles and radial partitions of the same number, both being some multiple of six. The polyps of a colony are all alike, and the hard matter they secrete is carbonate of lime. In the second subdivision, the Alcyonaria,—or halcyonoids, as they are commonly called,—the tentacles and radial partitions are always eight in number, and the tentacles have small symmetrical appendages or branches. The polyps of this group are often accompanied by small zoöids having no tentacles. The hard secretions are horny and elastic, as in sea-fans, sea-whips, and sea-pens, or they are extremely hard, as in Corallina rubrum.
These curious and, at times, beautiful creatures are polyps, and are constructed on the radial system. They have a cylindrical body with a broad base and rows of hollow tentacles around the upper disk. They have a central sac, and a space between the outer and inner sacs which is divided vertically by walls called mesenteries, as explained on page 114. Each tentacle, however many there [pg143] may be, has a corresponding chamber. The inner sac has a mouth, like a slit, at the top of the disk, opening to the outside, and it also has openings into the chambered spaces which surround it. These chambers also open into the hollow tentacles; thus a continuous circulation throughout the whole animal is established.
The food taken in at the mouth is digested in the inner sac, passes through all the chambers of the cavity as nutritive fluid, and is then expelled at the mouth again. The inner sac, or gullet, has longitudinal grooves; two of these are broad and deep, and correspond to the corners of the mouth. These are called siphonoglyphs. The sea-anemone is soft and contractile, and belongs to the only order of this class which does not secrete a skeleton. It has two sets of muscles, one of which extends from the base to the summit of the body and is placed on the dividing partitions. Sea-anemones are classified by the arrangement of the septa and the manner in which the muscles are placed upon them. The other set of muscles is arranged around the circumference of the column or body. Each tentacle is furnished with similar sets of muscles. The animal is sensitive, and at the least alarm contracts its body by means of these muscles, and quickly transforms itself from a beautiful, flower-like form into a shapeless, unattractive, inconspicuous mass.
The Actiniaria are developed from the egg. The eggs form on the edges of the inner walls (mesenteries), and when mature drop into the outer sac (gullet), and out of the mouth as ciliated spheres (planulæ). After swimming about for a time these attach themselves to rocks, and, conforming to the irregularities of the surface, secure a tight hold. The upper surface of the planula then becomes depressed and forms a gullet, and in time a complete animal is formed. The Actiniaria reproduce also by budding. A small protuberance or simple elevation of the body-wall appears on the side at the base, or in some species on the disk of the animal, which generally develops into a complete animal and at maturity falls away from the parent. Sometimes several anemones bud simultaneously from the same individual, and a third generation commences to bud at the same time from the immature young of the parent stock. The sea-anemones increase [pg144] also by self-division. In this case a constriction is formed, which gradually deepens and forms a complete partition of the body, and two individuals exist where originally there was but one.
The Actiniaria are carnivorous and very voracious. They feed on small organisms and on shell-fish and crustaceans, which they suck out of their shells. To secure their prey they are armed with an abundant supply of stinging-cells on the tentacles, and also with fine stinging-threads which are ejected from pores which are distributed over the whole body.
Sea-anemones vary greatly in color and form, and when expanded suggest flowers, but do not resemble the one for which they are named. They abound on every shore, the same genus often being found in widely separated regions. They are larger and more highly colored in tropical waters. Many of the species are littoral, and are found in the tide-pools of rocky caverns, on the under side of rocks, and on the piles of wharves and bridges at low-water mark. The majority of them are attached, but are able to change their location; others, Edwardsia and Cerianthus, swim about when young, and in the adult state burrow in the sand or mud, leaving only their tentacles exposed. Bucidium parasiticum is parasitic on the folds of the membrane which hangs from the mouth of the large jellyfish Cyanea arctica. Fenja and Peachia lie on the sea-bottom, with their bodies horizontal like a worm, the mouth-end and tentacles erect.
Adamsia palliata furnishes another example of commensalism; it lives on the back of shells, commonly the whelk, inhabited by hermit-crabs. Minyas is pelagic; it has a float at one end, and by means of its tentacles swims about freely.
A very few species only are described below, since these polyps are unmistakable, being always columnar bodies, with the upper disk more or less crowded with tentacles, and so brilliant in coloring and beautiful in form as to attract attention if found in the expanded state; otherwise they are easily overlooked.
Genus Metridium
M. marginatum. This is the most conspicuous and abundant sea-anemone of the northeastern coast. It is common from New York [pg145] northward, and is found near low-water mark in tide-pools, on the under side of large stones, in sheltered crevices of rocks, and on the piles of wharves and bridges. In contraction it is a broad, low cone, but when expanded is sometimes ten inches across the disk. Allied species found in Florida are eighteen inches in diameter. The column is smooth, cylindrical, and broader than long. At the top is a slightly elevated, thickened fold, and above this a deeply folded and frilled margin, with numerous fine, short tentacles, appearing like a fringe, which cover the upper side of the disk half-way to the oval mouth. The color is exceedingly variable; commonly the column is yellowish-brown, but it may be pink, white, salmon, orange, or dark brown, or striped or mottled with different colors. The disk and folds are lighter or flesh-colored, and the tentacles are of varying colors, usually grayish with tips of brighter colors. When irritated this species throws out from the column numbers of long, slender white threads (acontia), which are covered with minute stinging-cells. These organs of defense protect the animal from the attacks of many enemies.
Genus Rhodactinia
R. davidsii (Agassiz), Tealia crassiformis (Gosse), the thick-petaled rose-anemone. The color varies, being often bluish-green mottled with crimson, often bright cherry-red, with the thick tentacles somewhat lighter in shade, or flesh-colored. The animal is found in shallow water. It assumes various shapes, changing every few minutes. The tentacles are short, conical, and uniform in size; the column, the breadth of which is greater than its height, often has wart-like processes in longitudinal lines. The diameter of the disk is about three inches. Found from Cape Cod northward in tide-pools and on ledges covered with Fucus.
Genus Holocampa
H. producta. Its column, stretched to its full extent, is a foot in length and about an inch in diameter, but when contracted is much shorter and thicker. It has but twenty tentacles, and these have swollen tips. Rows of suckers extend the length of the column. It ranges from Cape Cod to South Carolina, and is found under rocks at low-tide mark, and also on sandy beaches, buried in the sand, with its tentacles only above the surface.
Genus Sagartia
S. leucolena, the white-armed anemone. It ranges from Cape Cod to North Carolina, and is common in Long Island Sound, being found at low-water mark on the under side of stones. The column is elongated, cylindrical, translucent, flesh-colored, with simple plain disk and long, slender, whitish tentacles crowded together near the margin. [pg146]
The coral resembles the sea-anemone and is a polyp constructed on the radial plan (page 113). It lives in colonies, but, unlike the hydroid colonies, each polyp of the community is a complete organism, and in the reef-building corals all the individual polyps of a colony are alike. The home of each animal is called a corallite, and the aggregation of many corallites is a corallum.
The corallite is composed of carbonate of lime secreted by the polyp, and, broadly speaking, may be called a skeleton. The secretion forms a basal plate and radiating partitions between the mesenteries in the cavity of the animal, and also surrounds the polyp like a cup. In some species this is a solid substance; in others it is like a network through which the animal substance (cœnosarc) of the zoöids of the colony is connected, as in Madrepora.
The polyps reproduce by budding and by self-division (fission), in a manner similar to that of sea-anemones. The way in which the budding or the fission takes place determines the shape of the colony, or corallum, which has a great variety of forms. In some species the budding is confined to certain individuals of the colony. In this case the branched forms result. When growth takes place by fission, hemispherical masses are formed, which are often perfectly symmetrical, as in the so-called brain-corals. In Astræa the polyps are inclosed separately, but in Meandrina fission is confined to the upper half of the polyps, so that a complex polyp is formed, with several mouths opening into a common stomach, making long serpentine furrows on the corallum.
Some of the genera of the second subdivision, the alcyonarians, differ materially from the ordinary idea of corals, as their framework is of a horny and more or less flexible material (chitin). Of these are the sea-fans, sea-whips, and sea-pens. The organ-pipe coral of the same subdivision is an example of an exceedingly fragile lime structure, while the red coral, Corallina rubrum, [pg147] the species so much used for ornamental purposes, has an exceedingly hard and stony character. The madrepore corals are called reef-builders, but not in the sense of constructors of reefs. They do not erect definite structures as bees do. It is the aggregation of the skeletons of the dead polyps, together with other agencies, which forms a reef. The coral polyps, though so minute individually, are almost infinite in numbers. It is estimated that the colonies rise one half of an inch in ten years.
Corals live at different depths in the sea. Those which form the base of the reef are the astræans, which do not live above a depth of six fathoms. They are characterized by little star-shaped spots on the corallum, the radial partitions meeting in the center of the spots, or corallites. Next above the astræans come the mæandrinas and the porites. The former have elongated openings which extend in waving furrows over the surface. The porites resemble astræans, but the pits are smaller, with fewer partitions, and the substance is more porous. Above these and capping the reefs are the beautiful branching and palmate madreporians, together with millepores, numerous varieties of sea-fans (Gorgonacea), and the calcareous seaweeds (nullipores), making a garden of beautiful branching forms of every shape and color.
The coral reef is as thickly inhabited by other living organisms as is the forest by birds and insects. Mollusks, worms, crabs, starfishes, and sea-urchins find resting-places there and work destruction to the coral masses, as they bore and penetrate the reef in various ways until large fragments of it are detached and either washed by the waves to places far from their foundation, or ground to sand, which, filling the interstices of the reef, adds to its solidity.
The living coral is quite different in appearance from the bleached skeletons commonly seen. The surface of the corallum is often soft and downy, from the numerous waving tentacles, and its coloring is vivid and varied. The madrepores are pink, yellow, green, brown, and purple. Tubipora, the organ-pipe coral, has green polyps emanating from its red tubes. White polyps in star-like form dot the branches of the red coral of commerce, Corallina rubrum. The whole mass of Helipora is bright blue, [pg148] and the beautiful sea-pens are both highly colored and phosphorescent. Owing to the fact that these brilliantly colored polyps were mistaken for blossoms, the recognition of their true character was long delayed, they having been ranked as vegetables until comparatively recent times.
With few exceptions, corals do not grow in water below the temperature of 68°, hence they are inhabitants of tropical and subtropical waters. The Florida Keys are coral reefs, and the species described below are to be found there.
Genus Oculina
Arborescent; corallites arranged somewhat spirally on branches and widely separated; branches compact between corallites. Each bud is for a time at the apex of the branch, but finally becomes lateral, and then gives off another bud from its upper surface, and so the stem lengthens. (Plate XLIV.)
Genus Astræa
The star-corals. The corals of this genus are hemispherical masses covered with small star-shaped pits, or corallites. Although the diameter of an astræa-dome may be twelve feet or more, it has only one half or three quarters of an inch of living coral on its surface, the rest being solid matter left behind as the polyps rose in growth. The colony increases by self-division. The septa meet in the center of the corallite, making star-like pits; the surface is comparatively smooth. (Plate XLIV.)
Genera Meandrina, Diploria
Corallum massive, hemispherical in shape, with furrows running in irregular lines over the whole surface. The peculiar serpentine form of the corallite is produced by the animal growing in one direction, fission being incomplete, and new mouths being successively opened until a line of them extends along a common stomach.
D. cerebriformis. This species is commonly known as brain-coral or brain-stone. The hemispherical shape, together with the peculiar serpentine corallites, makes its resemblance to the human brain very noticeable and the name unusually appropriate. This species, when living, is bright yellow. (Plate XLV.)
| PLATE XLV. | |
|---|---|
| Porites furcata and P. astræaoides. | Diplora cerebriformis. |
| Madrepora cervicornis. | Madrepora palmata. |
| Mycedium fragile. | |
Genus Madrepora
Some species of these corals appear like branches, while others have flat, low surfaces or fronds; all of them are covered with innumerable small cylindrical cups. Each cup is the home of a polyp, which secretes calcareous matter around its column, and septa between its radial partitions. The corallum, when examined with a glass, looks like meshwork. Through the fine openings of the porous surface, the polyps of the colony are connected by interlacing tubes of animal substance (cœnosarc). The polyps of the madrepore colonies are small in comparison with the connecting structure, which becomes very massive; but, although large, the corallum is fragile, on account of its perforated character and the exceeding delicacy of its parts.
In species which form incrustations, new polyps arise from tissue which spreads beyond the corallites. In some species certain polyps and corallites increase in length, growing longitudinally, and continually form buds around the base. This manner of growth leads to the formation of branches, while the former manner gives lateral extension. Both of these forms of budding may take place at the same time in the same colony. The madrepores are among the most common of the reef-builders. They form reefs which extend for miles around the Florida Keys.
M. cervicornis, the stag-horn coral. This is a branching species which attains large size. Its manner of growth is as follows: At the tip of each branch is an individual polyp, which is larger than those which surround the branch. This is the original animal which started the branch, and is the parent from which all the others on the branch have budded. The large terminal polyp buds around the base; a surplus of lime also collects at the base and clogs its tissues, so that it no longer can perform the functions of life, and after a certain period the base becomes dead matter. The polyp on the upper end continues to live and rises above the excess of solid matter. At the same time it continues to form new buds. The buds become independent corallites and secrete an excess of calcareous matter at their bases, which cements them to the parent stock and increases the thickness of the branch. Thus, as the original polyp constantly rises and buds, the colony assumes a stem-like form, covered with numerous individuals. Certain polyps on the main stem have the attributes of the parent animal. These start branches, and so the process goes on, and in time the colony becomes much branched and arborescent in form. In the living coral each little polyp is like a minute sea-anemone, having a colored cylindrical body surrounded on its upper disk with numerous tentacles. (Plate XLV.) [pg150]
M. palmata. This madrepore grows like the one described above, except that the branches do not remain separated, but unite or grow together, giving broad, flat surfaces which resemble fronds. When carefully examined these surfaces show striations which indicate the course of the branches. The structures forming the lobes are caused by the failure of the branches to unite. On the Carysfort Reef of the Florida Keys this species covers the top of the reef for several miles, nearly reaching the surface, and appears like a vast bed of low yellow shrubbery. (Plate XLV.)
Genus Astrangia
A. danaë. A small coral found on the New England coast. It lives in the clefts of rocks in small patches, sometimes two to three inches across and one quarter of an inch or more high. Frequently it is like a thin crust of lime covered with star-like divisions. Sometimes it forms branches. The living animals are white, and when expanded rise above the cells and resemble a cluster of small sea-anemones.
In this subclass—the actinoid corals—the polyps are of two kinds. The smaller are without tentacles and are called siphonozoöids. The larger have but eight radial partitions and eight tentacles. This limitation of parts places them in a higher rank than the corals of the first subclass. Another characteristic of these polyps is the presence of symmetrical branchlets on the tentacles, which give them a feather-like appearance. These corals are called halcyonoids. [pg151]
Some of them may easily be fancied to have been selected for halcyons' nests, as the name suggests—the sea-fans, for example.
Genus Alcyonium
A. palmatum. This coral community is found sometimes at low-water mark, but usually in deeper water, attached to shells and stones. It is commonly known as dead-men's-fingers, an unpleasant name given it by fishermen because of a fancied resemblance to a human hand with only the stumps of the fingers. The substance of the coral is semi-cartilaginous, with scattered spicules of lime which give it stability. When the polyps are fully extended the colony is rather attractive in appearance, but not so when contracted. It is found in abundance on the New England coast. An immense Alcyonium, Paragorgia arborea, grows on the fishing-banks off Newfoundland, and is sometimes brought up on the fishing-lines. It is tree-like in form, and measures six feet or more in length.
Genus Tubipora
The organ-pipe coral. This genus, which is deep red in color and very fragile, consists of many tubes slightly separated from [pg152] one another, but connected by horizontal platforms at short intervals. The form of reproduction, by budding, in this colony is peculiar to itself. The spicules of lime secreted in the polyp unite or fuse into a tube or cylindrical skeleton. At certain stages of development the polyp sends out a horizontal expansion, which unites with the expansions of other polyps and becomes calcified, forming a shelf which binds the tubes together. From the top of the platforms other corallites are formed, and thus a colony is made, which broadens as it rises in its growth. The body of the polyp is green, the skeleton red. It belongs to the East Indian seas and is given here only as an example of a peculiar manner of growth.
These are compound, tree-like Alcyonaria, with a calcareous or horny skeleton which forms a branched axis and is covered with a layer of united polyps having spicules of lime distributed through the mass, which give some firmness to the bark-like covering. Gorgonias, in great variety, grow in abundance on the coral reefs and mud-flats of Florida, forming masses of low shrubbery, pink, yellow, brown, or purple in color.
The sea-whips and sea-feathers are varieties of gorgonias, which are named from their forms. Some have shapes which resemble branching shrubs; others are long unbranched rods, either straight or spiral. They attain a height of several feet and are of various colors. The colony has a horny axis surrounded by a living mass which resembles a sheet of animal matter. This mass consists of polyps closely united, and has throughout its substance spicules of carbonate of lime, making it a kind of calcareous crust or bark. In dried specimens this becomes very brittle, and is easily broken from the horny axis. (Plates XLVI, XLVII.)
| PLATE XLVII. | |
|---|---|
| Leptogorgia rigida (a gorgonia). | Eunicea lugubris (a gorgonia). |
| Gorgonia flabellum (a gorgonia). | Leptogorgia Agassizii (a gorgonia). |
| Pennatula borealis and P. aculeata (sea-pens). | |
The sea-fans are colonies with a central, horny, flexible, and much-branched axis, covered, as in the sea-whips, with a layer of united polyps containing spicules of lime, which make a somewhat [pg153] firm crust. This, in dried specimens, breaks off readily. The colony branches profusely, or rather separates by fission, in one plane, the large and small branches making a network of fan-like shape and often of great fineness and intricacy. These fans attain a length of several feet and a corresponding breadth, and are abundant in semi-tropical as well as in more southern waters. In color they are red, yellow, brown, or purple.
These singular colonies resemble quill-feathers, such as are used for pens, and are named for this reason. The long, horny central axis is naked below, and is partly buried in the sand, but is not permanently attached. The upper portion of the axis has two rows of short, opposite, lateral branches; on the upper side of the branches the polyps live in separate inclosures. Spicules of lime are present in the substance of the branches, which gives them stability. Sea-pens are found at moderate depths and are widely distributed. They are highly colored and phosphorescent. [pg154]
These are delicate, free-swimming, generally spherical bodies, resembling jellyfishes in outline, transparency, and gelatinous consistency, but differing from them widely in the manner of locomotion. They are called "comb-jellies" from the rows of flat cilia, arranged like the teeth of a comb, which run in eight meridional lines over the surface. It is by means of these cilia that the animal moves through the water. The little paddles are worked in unison, in single lines, or each one of them can be moved independently, and they give the animal varying and peculiar motions. The Ctenophora are nearly transparent, but have a prismatic coloring, caused by the waving cilia, and at night they are phosphorescent. They are widely distributed, being found in all seas.
The mouth of the animal opens into a gullet which extends two thirds through the length of the body. On each side of the gullet is a vertical tube. The two tubes unite at the base of the gullet, and from there run as a single canal to the end opposite the mouth, and open to the outside through two excretory pores. From the base of the gullet, where the tubes unite, two other tubes extend laterally, which divide and subdivide in a horizontal plane, becoming eight in number, and connect at the surface with the lines of cilia; then, dividing, run in opposite directions to the poles of the spherical body. The animal derives its nourishment and air through this circulatory system. A nervous system is situated at the pole opposite the mouth, in a small area surrounded by cilia, in the center is an eye-speck, or lithocyst. [pg156]
Genus Pleurobrachia