Read Ebook: The Sea-beach at Ebb-tide A Guide to the Study of the Seaweeds and the Lower Animal Life Found Between Tide-marks by Arnold Augusta Foote

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The rock pools are natural aquaria, more interesting by far than any prepared by man. The possibilities of these little sea-gardens are beyond enumeration. The longer one studies them the more one finds. In them all classes of seaweeds and marine invertebrates may be found and their habits watched. The great beauty of these pools gives them an esthetic charm apart from the scientific interest they excite. Perhaps one may find here a sponge, and removing it to a shallow vessel of sea-water can watch the currents of water it creates. Several sponges of the same species placed in contact will at the end of two days be closely united. If the sponges are of different species they will not coalesce.

In the clefts and crannies of the rocks are various fine seaweeds, often of the red varieties, sea-anemones, hydroids, polyzoans, crustaceans, mollusks, and ascidians. Crabs will be snugly ensconced under projecting surfaces. Most species are more plentiful at the lowest-water mark, and many are found only at this point and below.

SANDY SHORES

On sandy shores the greater part of the inhabitants live under the surface. Many give evidence of their presence by the open mouths of their burrows, and some distinctly point out these places by piles of sand or mud in coils at the opening. Some tubicolous worms have their tubes projecting above the surface. The tubes of /Diopatra/ are hung with bits of shells, seaweeds, and other foreign matter. Some mollusks announce themselves by spurting jets of water or sending bubbles of air from the sand. The majority of the underground species, however, give no sign of their presence on the surface, and must be found by digging. Many of them go deep into the sand, and in searching for worms the digger must be quick- and expert, or he will lose entirely or cut in two many of the most beautiful ones, which retreat quickly and to the extremity of their holes at the least alarm. One can be a rambler on the sandy beach for a long time without being aware of the many beautiful objects which inhabit the subsurface of the sand. The curious crab /Hippa/ will disappear so quickly into the sand that one is hardly sure he has really seen it. The vast number of worms will surprise any one who searches for them by their variety, their beautiful color, and their interesting shapes. Here again a glass is requisite to appreciate the delicacy and beauty of their locomotive organs, their branchiae, and so on. The most common of the gasteropod mollusks on sandy shores are /Nassa obsoleta/, /Nassa trivittata/, and /Polynices heros/. The last are detected by the little mounds of sand which they push before them as they plow their way just below the surface. On more southern beaches, /Fulgur/, /Strombus/, and /Pyrula/ are the common varieties. /Olivella/, /Oliva/, and /Donax/, also inhabitants of sandy beaches, will quickly disappear when uncovered by the waves, being rapid burrowers. Most of the many dead shells on the beach will be found to be pierced with a round hole, which is drilled by the file-like tongue, or lingual ribbon, of /Polynices/, /Urosalpinx/, or /Nassa/, which thus reach the animal within and suck out its substance. Another similar species is /Polynices/ /duplicata/, which extends to the Gulf of Mexico, while /P. heros/ is not commonly found below Hatteras. Crustaceans are abundant on the sandy beach over its whole breadth. Some of the sand-crabs live above tide-mark. Among these is the fleet-footed /Ocypoda/, which is interesting to watch. Often they go in numbers to the water's edge and throw up mounds, behind which they crouch like cats, watching for whatever prey the tide may bring up. When unable to outrun a pursuer they rush into the surf and remain there until the danger is past. The wet sand is often thickly perforated with the burrows of the sandhoppers . These often rise about the feet as do grasshoppers in the fields.

/Hippa talpoida/ is a remarkable crab, somewhat resembling an egg. It is not likely to be seen unless searched for by digging at the water's edge. It burrows so rapidly that one must be quick to catch it after it is exposed by the shovel. In some places the tests of "sand-dollars" are common. The living animal may be found buried just below the surface at extreme low-water mark.

The sea-wrack drifted in lines along the shore will repay careful examination, for here will be found many things belonging to other shores and deep water. It is often alive with sandhoppers, which hop away while one searches for less common things. Often the most delicate seaweeds, numerous small shells, worms, polyzoans, etc., will be found there.

The surface of the sand-beach is strewn with remains of many species, usually beach-worn, but interesting nevertheless as examples of species one would like to find in better condition, but good specimens of which elude ordinary search or are unobtainable except by dredging.

Egg-cases form another class of objects which are often gathered with no idea of their identity. Of these the most common are the long strings of saucer-like capsules which contain the eggs of the mollusk /Fulgur/, those having square edges being the egg-cases of /F. carica/, and those having sharp edges those of /F. canaliculata/. Collar-like sandy rings contain the eggs of /Polynices/ , which are cemented together in this shape. The boys of Cape Cod call them "tommy-cod houses." Cylindrical piles of little capsules, sometimes called "ears of corn," hold the eggs of /Chrysodomus/. The irregular masses of small hemispherical capsules are those of the common whelk . The so-called "Devil's pocket-books" are the egg-cases of the skate.

MUDDY SHORES

On muddy shores the eel-grass grows abundantly, giving an appearance of submerged meadows. It is one of the very few flowering plants which live in salt water. In summer its little green blossoms may be seen in grooves on the leaf-like blades. Many animals live on and among eel-grass. Found upon it is the delicate gasteropod mollusk /Lacuna vincta/, and its eggs in little rings; the iridescent /Margarita helicina/, and /Nassa/, with its bright-yellow eggs in small gelatinous masses; also little worms in tiny flat spiral shells, compound ascidians in jelly-like masses, clusters of shelly or horny polyzoans, isopods, planarian worms, and so on. Scallops will be found at the base of the plants, and the common prawns are very numerous, swimming freely about. Mud flats and shores are the homes of many mollusks, especially of /Nassa obsoleta/,--which is the most abundant shell of any considerable size from Cape Cod to the Gulf of Mexico,--and of vast numbers of the tiny /Littorinella minuta/, which serve as food for fishes and aquatic birds. Clams and worms of all varieties are also abundant.

There are many varieties of mud-crabs, of which the most common are the "fiddlers," which honeycomb the banks and the surface of salt-marshes with their burrows. The common edible crab /Callinectes hastatus/ is plentiful in bays and estuaries. The sluggish spider-crabs hide beneath the surface of the mud and in decaying weeds and eel-grass. Hermit-crabs are plentiful here as well as elsewhere. /Panopeus/ is a sluggish crab found in shallow water and in all sorts of hiding-places along the shore. It may often be found in dead shells, and, in the South, in holes in the banks. This genus is represented by a number of species, some of which are quite pretty.

WHARVES AND BRIDGES

On the piles of wharves and bridges may often be found beautiful tubularian hydroids in large tufts just below low-water mark, branched hydroids looking like little shrubs, polyzoans, sea-anemones, mollusks, and ascidians. The species peculiar to these localities are the boring mollusk /Teredo navalis/, or ship-worm, the boring isopod /Limnoria lignorum/, and the boring amphipod /Chelura terebrans/, all of which penetrate the wood and are most destructive.

The animals and plants of tropical beaches and coral reefs are so various and abundant, so curious and beautiful, as to make a description or even an enumeration of them in a brief space difficult. The collector is bewildered and excited when he first views the profusion of the wonderful forms there found.

It is not generally known that a fine species of "stony coral" is common from Cape Cod southward, growing in clear water as an incrustation on rocks, and developing little spires as it advances in age. This species, the /Astrangia dana?/, is especially interesting, since it will live in a dish of clear sea-water, and the polyps will expand, showing a very close relationship to the sea-anemone. With care in changing the water this coral will live for days, and may be examined in its expanded condition with a lens of moderate power.

The most favorable time for collecting on any beach is at the lowest tide, many objects being then uncovered which do not appear higher up on the beach. At the spring-tides, which occur twice a month, at the period of the new and that of the full moon, the ebb is especially low, and affords an opportunity to search for forms whose habitat is below ordinary low-water mark. During storms deep-water forms are often torn from their beds and cast upon the beach. Shore-collecting at these times is often very interesting.

EQUIPMENT FOR COLLECTING INVERTEBRATES

PRESERVING INVERTEBRATES

To preserve specimens, they should first be placed in a weak solution of alcohol, the strength of which should be increased gradually until the animal is entirely free from water and is hardened throughout. If the alcohol becomes colored and sediment falls to the bottom of the jar, the animal is degenerating, and the alcohol should be changed. Specimens for transportation can be packed by wrapping each one in a bit of cheese-cloth and then placing them together in a large receptacle. Care should be taken to keep the fragile specimens separate. Sand-dollars possess a pigment which discolors and soon vitiates alcohol, and consequently these should be separated from the other forms and placed where the alcohol may be changed from time to time as appears necessary. The homeopathic vials containing small specimens may be put into the can without injury to the other specimens. Special cans of various sizes, with handles and screw covers, are made for naturalists. One of these cans is a convenient receptacle for carrying the alcohol to the station and for receiving the collection for transportation. Careful notes should be made on the spot of the conditions under which the species are found. One is likely to forget details if this is delayed until one reaches home. Labels should be used, giving name when known, or a number when the name is not known, corresponding with the note-book. Names written with lead-pencil on a slip of paper will not be defaced by or injure the alcohol. Collections when arranged permanently should be placed in glass jars, the species being kept separate.

COLLECTING AND PRESERVING SEAWEEDS

To collect seaweeds one must search for them on rocks, in tide-pools, in the sea-wrack upon the beach, on piles of wharves, on eel-grass, and on the surface of incoming waves. It is well to follow the receding tide and take advantage of its lowest ebb to search the extreme limit of the beach in the short time it is exposed. Many of the red seaweeds are found there.

The equipment for collecting consists of a basket, two small tin pails, one small enough to be carried within the other, a staff with an iron edge at one end and a small net at the other, and a pocket-lens. Rockweeds or other coarse gelatinous seaweeds should be put into the basket. The pails, half filled with sea-water, will receive the other specimens, fine and delicate algae being put into the smaller pail. It is well to have a second small receptacle for /Callithamnion/ and /Griffithsia/, if one can be further burdened. /Desmarestia/ should be kept apart, if possible, since it discolors and decomposes other algae; it should also have the earliest attention when the time comes for mounting, and salt water should be used for floating it upon the mount, otherwise the beauty of the specimen will be impaired.

Besides its use as a support, the staff is needed to dislodge specimens from the rocks, and the net to secure those that are floating just out of reach. When possible, it is desirable to secure the whole plant, including the holdfast, and to gather several plants of the same species, since they vary with age and other conditions, and it is also well to have duplicates for exchange. It is particularly desirable to obtain plants which are in fruit. Each specimen as it is taken should be rinsed in the sea-water to free it from sand.

Collections should be mounted as soon as convenient, and especial care in this respect should be taken with red algae, as they decompose quickly. The requisites for mounting are blotters, pieces of muslin, two or more smooth boards, weights, a basin, and several shallow dishes containing water. Fresh water has a strong action on the color and substance of seaweeds, and specimens should not be left in it for any length of time.

Lift a specimen from the general collection, and in a basin of deep water carefully wash off all superfluous matter; then place it in shallow water and spread it out, trimming it judiciously, so that when mounted it will not be too thick and the characteristics be hidden. Specimens are more interesting and their species more easily determined when laid out rather thin, showing their branching and fruit. After the specimen is thus prepared, place it in a second shallow dish of water. It should now be perfectly clean. Float it out into the desired position, spreading it well, letting some parts show the details of the branching, and other parts the general natural effect of the mass. Run under it a rather heavy sheet of white paper, and lift it carefully from the water. If raised from the center, it is easier to let the water subside evenly and gradually without disarranging the parts. Some collectors find it better to float the specimen in water deep enough to allow the left hand to be placed under the sheet to raise it. Lay the sheet on a plate, and with a needle or forceps rearrange any of the delicate parts which have fallen together. A few drops of water placed on any portion will usually be sufficient to enable one to separate the branchlets or ultimate ramifications. A magnifying-glass will be useful in this work.

Cover a blotter with mounted specimens, spread over them a piece of cotton cloth, and on this place another blotter, upon which lay more mounted specimens and a cloth. Proceed in this way until all the specimens are used. Lay the pile of blotters between boards, and on them place the weights. The weights should not be very heavy. Judgment must be used in assorting the specimens, those that are fine being placed together. Those that are coarse and likely to indent the blotters should be placed between separate boards. In this way a flat surface and an even pressure will be obtained. The blotters and cloths should be changed twice each of the first two days, then the cloths should be removed and the specimens left in press for a week, the blotters being changed daily. Be sure that the specimens are perfectly dry before placing them in the herbarium. Label each specimen with the name and the date and place of collection.

There are some seaweeds which cannot be treated in the above manner. /Fucus/ if placed in fresh water soon becomes slimy. It is so full of gelatine that it soon destroys blotters; therefore it is well to hang it up for several hours and then place it between newspapers, which should be frequently changed, and as the plant becomes pliable it should be arranged in proper position.

Those specimens which do not adhere to paper in drying should be secured with gum. When it is impossible to mount specimens at the time they are collected, they can be preserved by drying; afterward they can be soaked and mounted in the usual manner. To dry the plants, lay them separately upon boards without pressing out the sea-water, and leave them in an airy, shaded place until thoroughly dry; then pack them loosely into boxes and label, giving date and locality. Blotters or driers can be obtained at botanical-supply stores at thirty-five cents per quire.

HOW TO ARRANGE A HERBARIUM

The standard herbarium-paper is sixteen by eleven and a half inches. The sheets are single, white, smooth, and quite heavy. These, together with folded sheets of yellow manila paper, called genus-covers, are the only requisites. It is desirable to have also a case of shelves protected by glass doors. The shelves should be twelve by eighteen inches, and four to six inches apart. They are more convenient when made to slide like drawers.

The different species of one genus are gummed on one or more of the white sheets and placed within the folded manila paper, which serves as a cover. Each specimen should be signed with its name, place, and date of collection, thus:

/C. rubrum./ Bar Harbor. Aug. 12, 1899,

the generic name being indicated by its initial capital letter and the specific name written in full. To this are often added the name of the collector and some interesting comment. On the lower left-hand corner of the genus-cover is written the generic name in full and the species of that genus which the cover contains, thus:

/Ceramium/ /C. rubrum/ /C. strictum/ /C. diaphanum/

The genera of an order are then placed within a cover and labeled in the same way, the legend then having the name of the order on the left and the genera on the right of the bracket, thus:

/Rhodymeniaceae/, suborder /Ceramieae/

/Callithamnion/ /Griffithsia/ /Ceramium/

When the order is a large one the genera are distributed through as many covers as may be necessary. The covers are then arranged on shelves in the regular order of their classification, and each shelf is labeled with the order it contains. Herbarium-sheets cost at retail one dollar per hundred. Genus-covers cost at retail one dollar and eighty cents per hundred.

CLASSIFICATION

In broad generalization, objects of wide dissimilarity are recognized as belonging to the same kingdom, as do trees and grasses, or as do birds and fishes. Certain trees or grasses and certain birds or fishes have such points of resemblance that they plainly show that they belong to subdivisions. The most untutored people recognize these distinctions, but the naturalist goes further and finds points of distinction which the casual observer overlooks.

The animal kingdom has a varying number of divisions, called /branches/, /subkingdoms/, or /phyla/. Some late authors have admitted twelve divisions, and have given them the name /phyla/. Each phylum is composed of a group of animals with a plan of structure which is common to themselves, but differs from that of the animals of all other phyla.

The higher animals begin with the twelfth phylum, namely, the /Chordata/, or vertebrates. These animals have a spinal column, or series of vertebrae, while the lower animals, or invertebrates are without a spinal column, and depend for stability upon muscles or coriaceous or calcareous coverings. The vertebrates are first represented in the fish-like forms. Bilateral symmetry, however, or the uniform arrangement of parts on each side of a central axis, exists in several groups which are below the vertebrates, the first pronounced example being found in worms. Groups lower than worms have their organs arranged around a central axis or radiating from it, and were once all classed as /radiates/.

An animal is classified in accordance with its morphology, anatomy, histology, and embryology. Morphology determines its general shape, the position of its limbs, eyes, and mouth, and the covering of its body; anatomy, the arrangement of its internal organs, such as the position of its heart, lungs, stomach, etc.; histology, the character of the tissues of the body; and embryology, the method of the development of the animal from the embryo to maturity. It is only after these exact discriminations have been made that the groups are arranged. Owing to the greater accuracy resulting from histology and embryology , many changes in classification have been made, and as science advances will continue to be made.

The primary groups are based on broad general characteristics, but their divisions and subdivisions are determined by closer distinctions. Animals having shells differ from those having a cartilaginous or those having a crustaceous covering, and are placed in different groups. Yet mollusks having a single or a double shell, having spiral or flat forms, living on land, in fresh water, or in the sea, while differing from one another, are all of one group. Lobsters and crabs, although both have crustaceous coverings, are very unlike; and again, there are many species of both lobsters and crabs.

To group individuals, noting resemblances as well as differences, a system of classification has been arranged with the following divisions:

Kingdom, Phylum, Class, Order, Family , Genus, Species.

ANIMAL LIFE IN ITS LOWEST FORMS

The biological division, or discrimination, between animal and vegetable life, is based on the manner of assimilating food. Plants feed upon mineral substances, or, in other words, assimilate inorganic matter, while animal life requires for its support vegetable or some other organic matter.

Animal as well as vegetable life in its lowest forms begins with one-celled organisms, which are called respectively /Protozoa/ and /Protophyta/ . Both of these divisions are composed mostly of microscopic objects, and, together with other minute forms of life of the marine species, constitute a great part of the /plankton/, or free-floating organisms of the sea. These minute organisms seem like connecting-links between the two kingdoms. They were claimed by both botanists and zo?logists until the use of the microscope made close observation of minute structure possible.

Among the small animalcules of the phylum /Protozoa/ are some which are familiar to all by name, such as the /Infusoria/, which are most interesting creatures to examine in a drop of water under the microscope. A more tangible example of the /Protozoa/ are the /Foraminifera/. /Foraminifera/, like diatoms, have a shell-like covering, and these shells, among the most plentiful of which are those of the genus /Globigerina/, fall, as do those of diatoms, in immense numbers to the bottom of the ocean, and form respectively what are known as /Globigerina/ and diatomaceous ooze. In course of time the sedimentary strata become fossilized; thus, the stone of which the city of Paris is built consists of fossilized foraminifers, and the pyramids of Egypt are built of nummulites, another genus of /Foraminifera/. It is estimated that an ounce of this deposit contains four millions of these protozoans, so it is impossible to conceive the numbers of once living animals represented in the tombs of the Pharaohs. Telegraph-cables raised from the depth of two miles bring the message to naturalists that the bottom of the ocean at that depth is composed of little else than the calcareous shells of /Foraminifera/.

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