Chapter VII: Part II: Marine Invertebrates (2)

From the margin of the umbrella depend the tentacles. There are little mineral deposits, like crystals, called /lithocysts/, disposed at intervals on the margin, and known also as /marginal bodies/, which are supposed to be eyes. In some species these lithocysts are inclosed in club-shaped bodies, and they are then called /tentaculocysts/, because they are like small tentacles. These, together with the nerve-fibers, are called the sense-organs; but to what extent jellyfishes can see and feel is undetermined. This is the first appearance of sense-organs in animals. Around the concave surface of the umbrella is a muscular zone, or zone of contractile tissue, by which the animal opens and shuts the umbrella and gets its locomotive power. The /gonads/, which are conspicuous from being more opaque than the rest of the body, are the egg- or sperm-sacs. They vary in form and in position.

The jellyfish is carnivorous, feeding on small organisms such as crustaceans and even fishes. The tentacles are invested with stinging-cells, as are also the frills about the mouth, when such occur. With these stinging-cells, which are in some species so powerful as to have been compared with an electric battery, the jellyfish benumbs its prey. The stinging properties are due to nettle-like threads contained in poison-cells. When these penetrate the flesh they produce a pain similar to that of an electric shock.

The food is taken into the manubrium by the square mouth at its free end, and is there digested. It is then sent as nutritive fluid through the canal system of the body, and ejected through small pores in the canal which surrounds the margin of the umbrella.

There are two sexes. The gonads of the female contain eggs; those of the male, sperms. The contents of the gonads drop into the central cavity and pass out through the mouth. The fertilized ovum is called a /planula/, and is a transparent sphere covered with cilia, by means of which it swims about for a time. At length it attaches itself to some object, and becomes in some species a branching colony (hydroid), in other species a /strobila/. The latter, as it grows, is constricted at intervals, and at maturity resembles a pile of inverted saucers with lobed edges. Each of [pg136] these saucers is finally detached, and when liberated is called an /ephyrula/, and becomes a jellyfish. Thus its cycle of life is complete. There are some species which, having no hydroid or strobila state, mature without alternation of generation (/metagenesis/).

The term of life of the jellyfish does not exceed one year. Even the giant /Cyanea/ attains its immense growth in six months. It starts in the spring as an ephyrula, not more than one half of an inch in diameter, and when it dies in the autumn is often six to eight feet in diameter. The bodies of jellyfishes are ninety-nine per cent. water, and the dead ones thrown upon the beaches by the autumn storms rapidly disappear, leaving no traces behind.

The powerful stinging-cells with which the large medusae are armed make them formidable enemies, and it is probable that some deaths by drowning are caused by swimmers encountering them and becoming paralyzed by them.

ORDER =STAUROMEDUSAE=

("/Cross-medusae/")

GENUS ^Lucernaria^

^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.)

ORDER =PEROMEDUSAE=

("/Maimed medusae/")

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]

ORDER =CUBOMEDUSAE=

("/Cube-medusae/")

GENUS ^Charybdaea^

^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.

ORDER =DISCOMEDUSAE=

("/Disk-medusae/")

SUBORDER ~SEMOSTOMAE~

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 medusae 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 medusae 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 medusae, 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 medusae 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 planulae 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 strobilae, 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.)

SUBORDER ~RHIZOSTOMAE~

The =Rhizostomae=, 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
algae. These jellyfishes are common on the Florida coast, huddled
together on the sands of the coral reefs. (Plate XLIV.) [pg141]

TABLE SHOWING THE CLASSIFICATION OF THE ACTINOZOA DESCRIBED IN THIS CHAPTER

Class =ACTINOZOA=

Subclass =Zoantharia= (/Mesenteries numerous, usually in
multiples of six; tentacles unbranched hollow cones/)

Order =ACTINIARIA= (/The sea-anemones. Single; no skeleton/)

Genera Species

^Metridium^ ^M. marginatum^
^Rhodactinia^ ^R. davidsii^
^Holocampa^ ^H. producta^
^Sagartia^ ^S. leucolena^

Order =MADREPORARIA= (/The stone- or reef-corals. Colonies;
skeleton calcareous/)

^Oculina^
^Astraea^
^Meandrina^
^Diploria^ ^D. cerebriformis^
^Madrepora^ ^M. cervicornis^
^M. palmata^
^Astrangia^ ^A. danae^

Order =ANTIPATHARIA= (/The black corals/)

Subclass =Alcyonaria or Halcyonoida= (/Tentacles and mesenteries
eight in number; tentacles feathered, that is, with uniform
branches/)

Order =ALCYONACEA=

^Alcyonium^ ^A. palmatum^
^Tubipora^

Order =GORGONACEA= (/The sea-fans and sea-whips. Compound,
tree-like colonies, with horny axis, branching throughout/)

Order =PENNATULACEA= (/Free, phosphorescent; colonies, with
horny axis; polyps in lateral branches/)

^Pennatula^

[pg142]

CLASS =ACTINOZOA=

SEA-ANEMONES, REEF-CORALS, SEA-FANS, SEA-WHIPS, AND SEA-PENS

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 zooeids 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/.

SUBCLASS =ZOANTHARIA=

("/Animal-flowers/")

ORDER =ACTINIARIA=

SEA-ANEMONES

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 (planulae). 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]

ORDER =MADREPORARIA=

STONE- OR REEF-CORALS

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 (c[oe]nosarc) of the zooeids 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 /Astraea/ 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 astraeans, 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 astraeans come the maeandrinas and the porites. The former have elongated openings which extend in waving furrows over the surface. The porites resemble astraeans, 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 deg., 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 ^Astraea^

The star-corals. The corals of this genus are hemispherical masses covered with small star-shaped pits, or corallites. Although the diameter of an astraea-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.)

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 (c[oe]nosarc). 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. danae.^ 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.

SUBCLASS =ALCYONARIA= or =HALCYONOIDA=

In this subclass--the actinoid corals--the polyps are of two kinds. The smaller are without tentacles and are called /siphonozooeids/. 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.

ORDER =ALCYONACEA=

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.

ORDER =GORGONACEA=

SEA-FANS, SEA-WHIPS, AND SEA-FEATHERS

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.)

Eugorgia aurantica. Muricea specifera. Pterogorgia acerosa. Gorgonia anceps.]

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.

ORDER =PENNATULACEA=

SEA-PENS

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]

TABLE SHOWING THE CLASSIFICATION OF THE CTENOPHORA DESCRIBED IN THIS CHAPTER

Class =CTENOPHORA=

Order =CYDIPPIDA= (/Two tentacles, retractile into sheaths/)

Genera Species

^Pleurobrachia^ ^P. rhododactyla^

Order =LOBATA= (/Numerous lateral tentacles contained in a groove;
body compressed; two large oral lobes/)

^Bolina^ ^B. alata^
^B. septentrionalis^
^B. vitrea^

^Mnemiopsis^ ^M. Leidyii^

Order =CESTIDA= (/Ribbon-like form, from body being extremely
compressed in the vertical plane/)

^Cestum^ ^C. veneris^

Order =BEROIDA= (/No tentacles; mouth very wide; gullet occupies
greater part of body/)

^Idyia^ ^I. roseola^
^I. cyanthina^

[pg155]

CLASS =CTENOPHORA=

COMB-JELLIES

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]

ORDER =CYDIPPIDA=

GENUS ^Pleurobrachia^

^P. rhododactyla.^ A transparent spherical body, one inch to one
and a half inches in diameter, with eight combs or plates of flat
cilia extending from pole to pole. At one pole is the mouth, like
a slit, at the other a small area in the center of which is an
eye-spot. From the body hang two tentacles, half a yard or more
in length, fringed with cilia. The tentacles are very contractile
and can be rolled up or expanded with great rapidity; they take
graceful curves as the animal moves rapidly through the water.
/Pleurobrachia/ has a pink tint, and prismatic colors play over
it from the vibrating cilia. It is a beautiful and interesting
creature to watch. Found along the shores of Massachusetts and
Maine.

ORDER =LOBATA=

GENUS ^Bolina^

^B. alata.^ Slightly oval in form; lower part of the body divided
into two large lobes which hang below the mouth. Four of the
swimming-plates are shorter than the other four and terminate in
curious processes or short appendages called auricles. /Bolina/
is about two inches in length, and is very delicate, transparent,
and phosphorescent. Its contractile power enables it to vary in
outline to a considerable extent. It has a slow undulating motion,
and sometimes carries its lobes uppermost and open. Usually found
associated with /Pleurobrachia/ from Massachusetts northward.

^B. septentrionalis.^ Found on the northern Pacific coast.

^B. vitrea.^ A species found in Florida. [pg157]

GENUS ^Mnemiopsis^

^M. Leidyii.^ Resembles /Bolina/ in general form; often six to
eight inches in length; gregarious, thousands often being collected
together; exceedingly phosphorescent.

ORDER =CESTIDA=

GENUS ^Cestum^

^C. veneris^, Venus's girdle. This singular animal, although not
an inhabitant of our seas, has its place in this group, and is
shown here because of its very curious shape. In form it is flat
and ribbon-like. Sometimes it attains a length of five feet, while
in breadth it is but one or two inches. The mouth is midway in its
length and is opposite the sense-organ or eye-spot. On each side of
the mouth is a short tentacle which protrudes from a sac. Four of
the swimming-plates are small; the other four extend along the edge
of the body. /Cestum/ moves by contractions of the body more than
by the combs which fringe its edges. It is very transparent, with
a violet hue, and is so delicate that it is difficult to capture
it uninjured. Its habitat is the Mediterranean Sea. It may be seen
among the zooelogical specimens in almost any museum.

ORDER =BEROIDA=

GENUS ^Idyia^

^I. roseola.^ This species has an ovate body three to four inches
in height and about half as broad. Some individuals are larger.
It has [pg158] an eye-spot on the upper rounded side, and at
the other end a very large mouth opening into a digestive cavity,
which occupies the greater part of the body. A delicate fringe
surrounds the area about the eye-spot, and eight rows of cilia
run from there to the oral end. It has no tentacles. /Idyia/ is
pink and especially highly colored at the spawning-time. Like
other jellyfishes, their part in life is finished when they have
discharged their spawn, and the first September storms break them
to pieces. In July and August they are plentiful on the New England
coast. They appear at the surface of the water in the hottest part
of the day, but disappear entirely when the water is in the least
rough or the weather is cold or the sun overcast. Their movements
are slow and graceful, the long axis being carried in a nearly
horizontal position. They are exceedingly voracious, feeding
chiefly on other /Ctenophora/, and often swallowing animals as
large as themselves.

^I. cyanthina.^ This species, found on the northern Pacific coast,
broadens near the center, making it somewhat vase-shaped. /Idyopsis
Clarkii/, a similar genus, found in Florida, is globular. All these
species are very beautiful, the rapid movement of the cilia giving
them a brilliant iridescence.

III

WORMS
(PLATYHELMINTHES
NEMATHELMINTHES
ANNULATA)

TABLE SHOWING THE CLASSIFICATION OF THE WORMS DESCRIBED IN THIS CHAPTER

Phylum =PLATYHELMINTHES=

Class =TURBELLARIA=

Order ~POLYCLADIDA~

Genera Species

^Planocera^ ^P. nebulosa^
^Stylochopsis^ ^S. littoralis^
^Leptoplana^ ^L. folium^

Order ~TRICLADIDA~

^Planaria^ ^P. grisea^
^Procerodes^ ^P. frequens^
^Bdelloura^ ^B. rustica^
^B. candida^
^Fovia^ ^F. Warrenii^

Order ~RHABDOC[OE]LIDA~

Class =TREMATODA= (/External and internal parasites/)

Class =CESTODA= (/Internal parasites/)

Class =NEMERTINEA=

^Tetrastemma^ ^T. arenicola^
^Nemertes^ ^N. socialis^
^N. viridis^
^Meckelia^ ^M. ingens^
^M. rosea^
^Cerebratulus^ ^C. angulatus^
^Cosmocephala^ ^C. ochracea^
^Polina^ ^P. glutinosa^

Phylum =NEMATHELMINTHES=

Class =NEMATODA=

^Pontonema^ ^P. marinum^

Phylum =ANNULATA=

Class =CHAETOPODA=

Subclass =Polychaeta=

Order ~ERRANTIA~

Families Genera Species

~SYLLIDAE~

~APHRODITIDAE~ ^Polynoe^ ^P. squamata^
^P. sublevis^
^Harmothoe^ ^H. imbricata^
^Aphrodite^ ^A. aculeata^

~PHYLLODOCIDAE~ ^Phyllodoce^ ^P. gracilis^

~NEREIDAE~ ^Nereis^ ^N. virens^
^N. pelagica^
^N. limbata^

~NEPHTHYDIDAE~ ^Nephthys^ ^N. ingens^
^N. picta^

~EUNICIDAE~ ^Marphysa^ ^M. sanguinea^
^Diopatra^ ^D. cuprea^
^Arabella^ ^A. opalina^
^Lumbriconereis^ ^L. tenuis^

~GLYCERIDAE~ ^Glycera^ ^G. americana^
^G. dibranchiata^

Order ~SEDENTARIA~ or ~TUBICOLA~

Families Genera Species

~SPIONIDAE~ ^Nerine^ ^N. agilis^
^N. coniocephala^

~CIRRATULIDAE~ ^Cirratulus^ ^C. grandis^

~TEREBELLIDAE~ ^Thelepsus^ ^T. cincinnatus^
^Amphitrite^ ^A. ornata^
^Polycirrus^ ^P. eximius^
^Ch[oe]tobranchus^ ^C. sanguineus^

~AMPHICTENIDAE~ ^Cistenides^ ^C. Gouldii^

~MALDANIDAE~ ^Clymenella^ ^C. torquata^
^Maldane^ ^M. elongata^

~ARENICOLIDAE~ ^Arenicola^ ^A. marina^

~SABELLIDAE~ ^Sabella^ ^S. microphthalma^

~SERPULIDAE~ ^Serpula^ ^S. dianthus^
^Spirorbis^ ^S. borealis^

Subclass =Oligochaeta= (/Mostly terrestrial or fresh-water
forms/)

Class =GEPHYREA=

Order =SIPUNCULOIDEA=

Genera Species

^Sipunculus^ ^S. nudus^
^Phascolosoma^ ^P. Gouldii^

Class =HIRUDINEA= (/Leeches/)

[pg163]

WORMS

Burrowing in sand and mud, lying under stones and in crevices of rocks, concealed in various kinds of tubular cases which are free or attached to stones or shells, crawling over the ground or seaweeds, swimming free or attached to other animals, is found in abundance a class of animals commonly known as "worms," and generally regarded as repulsive creatures unworthy of attention.

To the biologist, however, worms are among the most interesting forms of lower animal life. The amateur collector, if he stops to give them careful consideration, will probably find them unexpectedly interesting, and will be surprised to find how many varieties of them there are, and how different they are from his preconceived notion of them. Worms are varied in structure, their habits are strange, and their form and color often beautiful. Although plentiful, they are not conspicuous, but are easily found if search is made for them, and so large a class of shore animals should not be passed by unnoticed. Unusual biological interest is attached to this group because, in the different types, affinities with other classes of animals are found, suggesting, perhaps, connecting-links with higher organizations. They are the first animals to show definite bilateral symmetry, or two similar sides, and to carry the same part of the body always in front. Formerly one division, called /Vermes/, comprised all the worms. To-day they are separated into four divisions, or phyla. The most careless observer easily recognizes the basis of separation, for the flatworms, the round- or threadworms, the wheel-like animalcules, and the jointed worms have very obvious differences. The names given the phyla express these distinctions, the termination [pg164] meaning "worm"; the prefixes /Platy-/, /Nemat-/, /Troc-/, meaning "flat," "thread," "wheel," respectively; while /Annulata/, meaning "ringed," describes the segmented forms belonging to that phylum.

There are vast numbers of parasitic worms, which live internally or externally on their hosts, there being no animal of land or sea, of high or low degree, which is not subject to the affliction of these visitors. The parasitic worms are degenerate, some being without digestive organs, or without eyes, or without locomotor organs, and so on, as the case may be, the host supplying the missing function. The life-history of these low forms is interesting; but parasitic worms do not come within the scope of this book, and are mentioned only to mark their place in the series.

PHYLUM =PLATYHELMINTHES=

FLATWORMS

The flatworms have a flattened body, more or less compressed in the different classes. Ordinarily the body is very thin, and, when short, has a leaf-like form; when long it is ribbon-like. Some species are thick in the middle and thin at the edges. They have a dorsal, or upper, and a ventral, or under, surface; a right and a left side; an anterior and a posterior end. The anterior end is carried forward and has some of the characteristics of a head, though a distinct head is not apparent. The mouth is on the ventral surface. In some species it is in the middle of the length of the body; in others it is before or behind this point.

The flatworms are the first animals to assume pronounced bilateral symmetry. They are soft-bodied, having no supporting skeleton, and they have no segments, or divisions, such as are found in higher types, as in /Annulata/. They have no body-cavity, the space between the organs and the body-wall being filled with tissue. The alimentary canal has no anal aperture, the excretions being carried off by a water-vascular system consisting of branching vessels which end in minute bundles of vibrating cilia, called ciliary flames. These flames communicate with the exterior through small pores or flame-cells. Their sense-organs are eyes [pg165] and otocysts. The latter are sacs containing crystals of carbonate of lime, and their function is supposed to be that of hearing.

The flatworms are hermaphroditic, and their propagation is by means of eggs. They are numerous and very generally distributed, occurring in fresh and salt water, on land and shore, on the surface and in the depths of the sea. A vast number also are parasites and infest, internally or externally, nearly every living creature. The parasitic forms differ anatomically from the free-living worms. The internal parasites, living by absorption of the digested food of their hosts, have no digestive organs; they are also devoid of organs of sense and of defense. The external parasites, being carried about by their hosts, are without organs of locomotion.

CLASS =TURBELLARIA=

The turbellarians are the simplest group of bilateral animals and occupy the lowest place among worms. They owe their name to the fact that they are covered with cilia, which are constantly in motion and cause a slight turbulence in the water around them.

ORDER =POLYCLADIDA=

("/Many-branched/")

The polyclads are found below half-tide mark on the under side of stones and on seaweeds. Sometimes they are found swimming about at night. They are leaf-like in form, one inch to two inches in length, and are very thin and delicate. They adapt themselves to the inequalities of the surfaces to which they attach themselves, and often are of the same color, and therefore are so inconspicuous that they are apt to escape notice. They move with a gliding motion over surfaces, and often swim when in search of food.

The intestine is much branched and has no anal aperture. From the mouth, which is placed in the center of the ventral surface, a pharynx, or muscular fold, is protruded in some species, which enables the worm to attach itself to and consume prey of considerable size. After digestion has taken place, the fecal [pg166] matter collects in the main intestine and is forcibly ejected by the pharynx. Numerous eyes are collected in groups on the anterior dorsal surface, or arranged around the margin of the body. The eggs are laid in shell-like cases, and cemented together in plate-like masses or in spirals, and attached to shells or stones. (Plate XLVIII.)

GENUS ^Planocera^

^P. nebulosa.^ One half of an inch wide and three quarters of an
inch long, circular or elliptical in shape; very flat and thin;
olive-green on the dorsal surface, with a line of darker color on
the posterior end, and whitish retractile tentacles on the back.
Found creeping on under side of stones in tide-pools.

GENUS ^Stylochopsis^

^S. littoralis.^ About one half of an inch long; changeable in
form, from broad oval to elliptical; color pale green, veined with
a lighter shade on the dorsal side, flesh-colored on the ventral
surface; numerous eyes arranged in irregular rows near the margin
and in groups in front of the tentacles, also clusters of eyes on
the tentacles. Found under stones between tide-marks.

GENUS ^Leptoplana^

^L. folium.^ Body flat; margin thin and undulated; shape leaf-like,
but changeable; about one inch long and one half of an inch wide;
color pale yellow, veined with a deeper shade; eyes in four groups
near the anterior end.

ORDER =TRICLADIDA=

("/Three-branched/")

The triclads are divided into three groups: those of the fresh-water ponds and streams, those of the land and sea, known as planarians, and those of the sea. The planarians are the most interesting worms in the order. The triclads differ from the polyclads in being elongate in form and in having the intestine in three branches instead of in many. The mouth is midway in the length of the body, on the ventral side, and from it protrudes a pharynx, which is cylindrical or bell-shaped, and is capable of great dilatation. With the pharynx the worm, which is wholly carnivorous, envelops other worms, crustaceans, or any animal food. Several species are found on the under side of stones in tide-pools.

GENUS ^Planaria^

^P. grisea.^ Oval or elliptical in form; anterior end truncate;
posterior end rounded; color yellow or gray, with a light stripe;
two black eyes surrounded with white; length one half to three
quarters of an inch; width about one eighth of an inch. Found under
stones between tide-marks.

GENUS ^Procerodes^

^P. frequens.^ One eighth of an inch long; brown or black above,
gray below; has two kidney-shaped eyes; active and abundant. Found
under stones near high-water mark.

GENUS ^Bdelloura^

^B. rustica.^ Body milk-white, smooth, thin. Found on /Ulva
latissima/ (sea-lettuce).

^B. candida.^ Parasitic on the gills of the horseshoe-crab.

GENUS ^Fovia^

^F. Warrenii.^ Bright red, narrow, oblong. Found on eel-grass.

ORDER =RHABDOC[OE]LIDA=

Minute, active worms found among the red seaweeds. They are brown in color, and are marked by one or more transverse white bars.

CLASS =NEMERTINEA=

The nemerteans are long, narrow, flat, smooth worms, and vary from one half of an inch to many feet in length. They are exceedingly contractile, and when alarmed can shrink to less than half their normal length. They are very generally distributed, and are to be found between tide-marks, in loose coils like a string, under stones on sandy and muddy shores. The very long species, like /Lineus marinus/, are solitary, but other smaller species are gregarious, many worms being coiled together in tangled masses. Some species are to be found in empty shells, and others live among the seaweeds. They are very slimy, the epidermis secreting an abundance of mucus, and they can often be tracked by the trail of slime they leave behind them. This mucus sometimes hardens, forming for some species a tubular [pg168] covering; others remain naked. All are covered with vibrating cilia, which is a universal feature of flatworms. In color they may be white, yellow, green, red, purple, etc., and sometimes they are banded or striped with a contrasting color. The ventral is usually lighter than the dorsal surface.

The principal characteristic of the nemertean worms is a long thread-like organ, known as the /proboscis/. This lies in a sheath along the center of the dorsal surface, and is quickly thrown out to a great length, and as quickly completely withdrawn within the body. The proboscis is slender, hollow, muscular, and full of nerves. It reaches the outside through a pore at the anterior end of the body, and has no connection with the alimentary system. It is used as a feeler and as a weapon. Some species have a sharp spine at the end of the proboscis, others have stinging-cells. The proboscis is sometimes so forcibly ejected that it breaks off, in which case it retains its vitality for some time, and seems as if it were itself a worm. A new proboscis is quickly grown by the worm to take the place of a lost one. The head is a little broader than the body, and has eyes arranged in one or several pairs on each side. The mouth is on the ventral surface, near the anterior end, has thick lips, and is very dilatable. Through the mouth the animal ejects a part of the esophagus and envelops its prey, which is often of considerable size. Chaetopod worms they often swallow whole; the soft parts, after being digested, are carried off through the regular passages, ending in the ciliary flames (page 164), while the indigestible parts are ejected at the anus. Often the spines and bristles find their way out by perforating the intestine and the body-wall, without apparently doing the worm any injury. The perforated parts quickly heal.