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THE HORSESHOE CRAB AND OTHER DENIZENS OF SAND AND MUD
THE horseshoe or king crab is an interesting beast, the sole survivor of an ancient and high-born lineage. Ancient in that it is related to the trilobites, highborn because it suggests an alliance with the curious ostracoderms. The first of these, the trilobites, are found in the rocks of the Cambrian period, the most ancient of all fossil‑bearing rocks, and they became an important race in the lower Silurian age, only to dwindle and die out before the Palaeozoic times ended. Incidentally we may learn a lesson from their fall as well as from the fall of other groups of animals now extinct, for they all, like the ancient Romans, indulged in bizarre and extravagant developments just before their decadence. The ostracoderms form a strange group of animals that flourished in the Devonian period, and, while neither fish nor crab, they combined certain features of both. To these relations of our humble horseshoe crab is given, therefore, somewhat tentatively it may be, the distinguished honor of being the progenitors of the vertebrates, of linking this highest group of animals with the lowly invertebrates, of bridging the yawning chasm between the back-boned and the back-boneless.
ROCK CRABS AND THEIR TRACKS
When one meets a horseshoe crab, therefore, it is well to treat him with respect for the sake of the trilobite and the ostracoderm with their strange histories. His days are probably numbered, for, although he is abundant in these regions, there are only two living species left in his class, one, this friend of ours of the marsh and beaches, which extends its range from Maine to Mexico, the other, a species that lives on the eastern Asiatic coast.
In the early part of the summer these strange beasts are busy depositing their eggs in all the sandy and muddy estuaries. They go about in pairs, the larger female, often dark and weather beaten, followed tenaciously by the smaller male. Later in the summer the high tides float up the delicate empty shells of the young horseshoes in hundreds on the marsh, for, like all crabs, growth is accomplished only by splitting and shedding the outside skeleton or shell. From this discarded cuticle emerges a soft-shelled and helpless individual. In this state, however, they are not often found, first, because the stage is short, and secondly, because they remain concealed until they harden sufficiently to brave the rough world. When in the usual condition they are provided with a weapon, which, for a bare-footed man at least, is most formidable. I refer to the long terminal sharp-pointed spine or tail, which they can erect at will. The horseshoe is a fair swimmer and walker, and advances straight forward, disdaining the indirect methods of true crabs, and it burrows deep in the sand by pushing its rounded front under the surface.
The beach flea, he of the large eyes, a plump, clean, shrimp-like creature about half an inch long, owes its name to its hopping powers only, — for it does not bite the living but only the dead. It is one of the most important beach scavangers, and dwells in holes from eight to ten inches deep near high-water mark.
In the early morning, before the sun has dried the sand or the wind blown it away, one may see a continuous city of conical mounds made by these little workers stretching in a band along the upper beach. If one can lose all sense of proportion, a state of mind easily acquired by viewing these mounds on the ground glass of a camera, they suggest pictures of the mounds of white ants, or of the tents of an encamped army. As the waves of the flood tide wash away these erections, the water, entering the holes of the beach flea, expells air which bubbles up for several seconds at a time, leaving multiple craters like those of the moon. In the daytime this crustacean rarely ventures abroad, but at nightfall the upper beach is fairly alive with their little plump forms, hopping about, seeking what they may devour. Their night of feasting and play over, they dig their holes, in which they remain for the day.
Another beach flea, a smaller, browner creature, exists in immense numbers in the sea-wrack of the beach, where it serves both as a scavanger and as a food for shore birds, — two very laudable purposes, but not equally appreciated by the beach flea.
Another little crustacean that I will call the beach sow-bug, as it lacks a common name, is flattened from above downwards instead of from side to side, like the beach flea, and makes interesting wandering marks between tides, for instead of hopping like its nimble cousin it progresses very slowly below the surface. Similar marks are made by periwinkles and other small mollusks, while the clam-worm writes its name in the same way but more plainly.
The clam-worm is worthy of more than passing notice, for, if one looks fairly at it, it is not a disgusting beast but one of considerable beauty. Indeed it is called scientifically a sea nymph. It is often a foot or more in length, of a bluish green color and somewhat iridescent, and it is provided on each side of its flattened body with innumerable bristle-bearing legs. It is a voracious creature, and comes out of its burrow in the sand or mud to feed on other worms and on small shrimps and snails, which it captures with a pair of horny notched jaws that are kept concealed in its gullet until needed.
While on the subject of worms, I must mention the sea-mouse, an extraordinary worm from three to six inches long, which is occasionally cast up after a storm on the beach. Its broad back is so thickly covered with bristles that it appears to be clad in fur and remotely suggests a mouse.
MOUNDS MADE BY BEACH FLEAS
CIRCLES MADE BY THE GRASS BLOWN BY THE WIND
The green crab, called by the scientific crazy — moenas — and by the French enragé, on account of its lively behavior and reckless audacity when brought to bay, is fonder of the milder water south of Cape Cod, where the gulf stream meanders, than it is of the shores washed by the arctic current. In the summer of 1901, however, it appeared in scanty numbers in the waters of Fox Creek, a tributary of the Ipswich River. The next year it had spread to the Castle Neck and Essex Rivers and was reported as far north as Kittery in southern Maine, while in the summer of 1903 it was abundant everywhere in the creeks, marshes and beaches. The winters, for some time mild, took on an arctic severity in 1903-4, and I was unable to find, any green crabs the following summer. Milder winters have followed, and by 1910 this crab was fairly abundant again. Although green in color with yellow markings when alive, it becomes reddish when dead and cast up on the shores, but its shape easily distinguishes it from the common rock crab. Whether it has established itself firmly here or has made but a transient extension from its more southern home I do not know.
Our own common rock crab, notwithstanding its name, is an abundant frequenter of these sandy shores, both on the outside beaches and in the more sheltered estuaries. It is fully as lively as its crazy cousin, and at dead low tide one can quickly pick up a basket full in the shallow waters if he is skilled in avoiding the nipping claws — otherwise it will be a long and painful process. It has a habit of burrowing in the sand of the beach, where it remains concealed, with the exception of a narrow crevice in which may be seen its watchful eyes. The gulls often find them there, pull them out and batter them to pieces. They are good eating — almost equal to the lobster, which is comparatively rare here.
Occasionally one notices a rougher, more massive looking crab, otherwise similar to the rock crab. This is the Jonah crab, the origin of whose suggestive name is to me unknown.
The sea-urchin, lover of rocky bottoms, is only occasionally thrown up on these sandy shores. When I meet him I wonder why I can always recall his elaborate name, Strongylocentrotus drobachiensis, with such readiness, when for the life of me I often fail to connect Mrs. Brown or Mrs. Jones with their somewhat simpler cognomens. Strongylocentrotus, however, is an old friend of mine, and years ago, when I combined the study of marine invertebrates with ornithology as a member of the Champlain Society at Mount Desert, I used often to bring up a dredge packed full of sea-urchins.
These spiny balls suggest Shakespeare, for Shakespeare calls a hedgehog an “urchin.”
“Ten thousand swelling toads, as many urchins,”
and to this day the dwellers in Warwickshire, through which the Avon flows, call the hedgehog “urchin,” and is not the sea-urchin as bristly as a land-urchin? Broken pieces of sea-urchins are not uncommon on the sides of the marsh drumlins, where they have been borne by crows and gulls and dropped from a height to break their shells, a fate that is abundantly meted out to the large sea-snails by the same birds.
Another member of this group of echinoderms is the sand-dollar, which delights in sandy bottoms and is found at and below low-water mark on the outer beach. Like the rock crab it burrows in the sand, but reveals its presence there by a slight circular elevation of the beach. In life it is covered with short spines, which give it a brown color, but to most persons its bleached and spineless cases thrown up on the upper beach are more familiar.
The more distinctly five-rayed members of this family, the starfishes, are in places abundantly represented on these shores below low water by the common starfish and by the Forbes’ starfish. The latter resembles the common kind very closely but is easily distinguished from it by its light orange madreporic plate — the porous stony plate through which the sea water enters the wonderful system of canals that end in the innumerable foot tubes by which the animal drags itself along. Starfishes are ravenous creatures, and have a habit of protruding part of their stomachs and sucking in their prey. They are much disliked by oyster men, who, it is said, used formerly to cut up any starfishes they caught and throw them overboard, not realizing that an arm with a portion of the body attached will, by pushing out new arms, become a new individual. Thus they increased rather than diminished their enemies. It is common to find individuals with one or more baby arms just appearing to take the place of those lost by accident.
If one takes the trouble to examine the great devil’s aprons that are thrown up on the beach after a storm, he will find among the powerful root-like extensions from the stem, which are fastened tightly to a mussel or stone, a veritable museum of lowly marine life. Among these are not infrequently to be seen some odd-looking starfishes with distinct disk-like bodies and spider-like arms which break easily on handling. These are the so-called “brittle-stars,” and if they are uninjured by their shipwreck, they will wriggle about actively and actually break off one or two of their legs in their desire to escape. It would almost seem as if they were inspired with the same object that leads lizards to shed their tails in order to distract their pursuers from the real thing.
As the tide ebbs one often finds on the sand — but not denizens of it, as the heading of this chapter would imply — the once free-swimming jellyfishes. They are sadly bedraggled by the waves, and entirely lack the graceful form and throbbing rhythmical movements which so excite our wonder when the animals are at home on the surface of the sea. The commonest of these is aurelia, with its transparent bluish-white disk eight or ten inches in diameter, and its group of four sacs in the middle, conspicuously straw colored or yellow in the females and pinkish in males. In the early part of the summer these jellyfishes swim strongly, and generally avoid the beach, but towards the end of the summer they become old and feeble, and are more often cast ashore. At this time the strange looking young, which are retained in the folds under the disks, are set free and attach themselves to rocks or seaweed, where they develop into little saucers piled one above the other, to be released and become veritable jellyfish the next spring.
Less frequently the large red arctic jellyfish is thrown up on the beach, looking like a great disorganized mass of coffee jelly. In its prime at sea this is a wonderful animal, as it has been known to measure seven and a half feet across the disk, and to have tentacles more than one hundred feet long. These same Medusa-like tentacles are to be avoided like the Gorgon’s locks, for they are plentifully supplied with lasso-cells, which sting the naked skin as with nettles.
Among the collections of delicate and graceful seaweeds that are carefully spread out and dried by the amateur, one often finds beautiful silvery, branching specimens, which are in reality not seaweeds at all, but hydroids, humble relatives of the jellyfishes we have just been considering. On close examination one sees a multitude of little horny caps attached to these plant-like stems. They are great colonies of animals living together, and are not far removed from the corals.
A still more lowly group of animals, several of whose representatives are thrown up on the beach, is the group of sponges often considered plants, but which the great Aristotle rightly contended were animals. These northern sponges are, however, lacking in the elastic qualities which make the sponge of commerce so valuable, for, when dry, they are brittle and easily pressed to powder. The commonest species is the finger sponge, which is orange-red in color when the animal is alive, but which later bleaches to gray or white. Its powerful sulphurous odor when brilliantly colored is apt to discourage the attempts of amateurs to preserve it. Another common species is appropriately called the bread sponge, for it looks for all the world like a piece of soggy bread. It is generally about the size of a small muffin, but I once found one as large as a ten-cent loaf.
A whole book could be written on the group of mollusks, or indeed on any of the groups of marine animals, but the true shell-fish are more abundantly represented in number of species than any other group. A few of these only can be considered. Like the horseshoe crab, the great sea-snail, scientifically known as Polynices, — the son of Oedipus the tyrant, — pushes the sand along in a little mound as it advances below the surface. When it is moving on the surface, one is astonished at the large size of the animal, with its immense foot, as the portion on which it creeps is called, and wonders how it can possibly retire into its shell. If one picks it up, it at once pours out water as from a watering pot, rapidly shrinks in bulk, and not only draws its entire body into the shell, but shuts the door after itself with a tightly fitting, horny operculum. This sea-snail, like all dwellers in or near the sea, has a tremendous appetite, and devours all sorts of game, dead and alive. It is particularly fond of other members of the same group of mollusks, and, in order to suck out their insides, it has a habit of boring a little hole through their shells as smoothly as if it had used a drill. This it does by means of a fleshy ribbon armed with rows of teeth that it conceals in its mouth, an instrument known as the lingual ribbon. Everywhere along the beaches curious sand collars, as the children call them, are to be found. These are shaped like the small boy’s broad collar and are open in front. When wet they are flexible, and, if held up to the light, they are seen to be studded with small, round transparent bodies. These are the eggs of the sea-snail, and she makes for them these curious egg cases of sand granules firmly glued together.
Lining the beach in windrows are generally to be found the pretty shells of another mollusk, which I shall call the wicker-basket shell, for that is the translation of its Latin name. Nearly all these shells are bored, and there is reason to believe that they are the victims of their own brothers and sisters, for like the son of Oedipus, the tyrant snail, they are provided with lingual ribbons, fierce appetites and loose morals.
It is a relief to turn to a vegetarian mollusk, and one which has a common English name. I refer to the periwinkle, — the same that Leech’s delectable Tom Noddy enjoyed eating with a pin on the top of a London bus. Indeed, the great ugly, dingy gray European periwinkle now swarms along our coast, and is crowding out the smaller, brighter-colored and more delicate native species. It is the English sparrow among mollusks.
Another univalve which is common to both sides of the northern Atlantic is the “purple” snail, whose shell is white or yellow or brown, plain or banded. If one has ever broken this little mollusk, and used it for bait, he will remember how deeply crimson stained became his fingers. In former times red must have been called purple, as witness the purple finch, which is red, and the old Tyrian purple, which was crimson, and was indeed obtained from near relatives of this same “purple” snail. Another snail of wide distribution that is found on this beach is the whelk. In England it is cooked and eaten.
So much for the shells with one valve, the gastropods as they are called, because they walk upon their stomachs. The shells with two valves are equally numerous on this coast, and we can begin with the edible mussel, the blue mussel that is common to both the European and the northern part of the American coast. Abroad it is an important article of diet, but in wasteful America it is as yet almost totally disregarded. It occurs in great blue-black beds in the tidal estuaries, where it is held in place by tough fibrous threads called the byssus. Although its yellow contents are scorned by most Americans, it is much appreciated by certain sea ducks, especially by the great group of scoters, who swallow the mussels shell and all, and grind them up in their powerful gizzards.
The sea mussel is a stouter, larger species with variously colored shells, and these are generally cast up on the beach after a storm, tightly embraced in the roots of large devil’s aprons. Another mussel which lives partly embedded in the mud or peat of the salt marshes is the ribbed marsh-mussel.
The empty shells of the razor-fish are common objects on the shores of the estuaries. They are long and narrow and sharp on the edges, all of which characters probably account for the name. They live in burrows in. the sand near low-water mark, and are able to descend with such rapidity to a depth of two or three feet that one must be a rapid digger to catch them. By approaching quietly and making a sudden thrust with the spade obliquely below them, one may sometimes cut off their retreat. The method of their descent is interesting, and easily observed in a captive razor. The foot is thrust downward into the sand in a point, and then expanded at the end into a bulb or disk, which acts as an anchor so that the animal can pull itself down. The act is rapidly repeated, and the razor soon disappears from sight.
Thrown up on the outer beach after storms one often finds the thick, heavy shells of a mollusk that is shaped like the little-necked clam or quohog, but it is larger than that bivalve as usually served on the dinner table, Its scientific name is suggestive of the north, for, being translated, it is called the “Icelandic Arctic.” It has no common name, but it may be called the northern quohog from its resemblance to its more southern relative.
Still more common on the beach are the delicate valves with greenish-yellow and highly glazed epidermis of Count Yoldi’s shell.
But perhaps the most conspicuous dead and empty shells that are to be seen thrown up on the outer beaches are those of the sea-clam, or giant clam, as they are sometimes called. These are the kind one finds in farmhouses on the coast wonderfully decorated with pictures of lighthouses or of vessels floating on blue waves. This clam is from five to seven inches long, white within and without when dead and weather beaten, but covered on the outside when alive with a pale brown epidermis. It lives close to low-water mark and so near to the surface that it is easily dug with a short stick or the fingers. The clammer walks along with a clam fork and prods every suspicious hole or slight elevation of the sand. If the clam is there, its tough, hard shell is easily detected and soon brought to view. An expert can follow an amateur over the same stretch of beach and find six to his one. I remember years ago riding a bronco pony along a lonely beach on Cape Cod, and jumping off whenever I saw signs of one of these clams. As far as I know this form of clam hunting is unique. It takes but a few of these great clams to make a chowder of ample proportions and most excellent flavor.
But after all the most famous bivalve of these shores, one which in its turn has made Ipswich famous, is the clam, — sand clam or soft-shell clam. Here indeed it is a sand clam, and its shells are thin and white and clean, and its flesh clear and transparent, very different from the dirty and dwarfed clams that are to be found in black dock mud. According to John Winthrop the clams at Ipswich feed only on the white sand! Much has been written on this mollusk, and its charms have even been extolled in verse. An Ipswich poet, in reviewing the attractions of his native town, ends his list as follows:
Whelk Sea-Snail Wicker-Basket Snail
Periwinkle Purple Snail Black-footed Snail
Northern Quohog Sea Mussel Common Clam Marsh Mussel
Edible Mussel Sea Clam Count Yoldi's Shell Razor Shell
William Wood says of these New England clams: “Clamms or Clamps is a shelfish not much unlike a cockle, it lyeth under the sand, every six or seaven of them having a round hole to take ayre and receive water at. When the tide ebs and flowes, a man running over these Clamm bankes will presently be made all wet, by their spouting of water out of those small holes: . . . In some places of the countrey there bee Clamms as big as a pennie white loafe, which are great dainties amongst the natives, and would bee in good esteeme amongst the English were it not for better fish.” He also speaks of the Indian squaw,
The digging of clams is indeed free, but at times much bitterness and some blows have resulted when the inhabitants of one town encroach on the clam flats of a neighboring town. The clam digger is a picturesque individual. He always appears to be solitary, even if there are a number working together, for each is bent and silent, intent on his own work. With a short rake with long teeth or a fork they skilfully dig up a square foot of sand, which falling down reveals the white clams. An amateur is sure to stick the fork through the clams, or to break them in raking them out, and to cut his fingers with the sharp edges. With the expert the clams seem to lead a charmed life, and escape intact into the hand and thence into the coarse, shallow clam-baskets, which are then soused up and down in the salt water to free the clams from the adhering sand. Nowadays the clammers reach the flats in motor boats, — noisy and vile-smelling, — which, sad to say, have all but displaced the dories in which they formerly rowed, or sailed if the wind was fair, to and from their work. Occasionally the clammers live in weather-beaten huts near the flats, and take their spoil to the towns. One such clammer lived a solitary life on the edge of the dunes, varying his shell-fish diet with an occasional sea-fowl. But alas! he loved the bottle, and one day his dory was found containing clam-baskets and fork, but nothing was ever heard or seen of him more. A clouded brain, a misstep, the swirling tide, and the vast sea, — it is a common fate and an all too common cause. A few days after this a fortune of great proportions to such simple folk was left to this poor man. But it was well that his end came as it did, for he might else have died in some gilded saloon, and had an ordinary burial, instead of the soft sand of the sea floor, and the free dirge of gulls and waves and storm.
In the highest group of mollusks, those which occur in the group of “feet around the head,” belong the nautilus and the cuttlefish. Of these only the small squid is found hereabouts, and it is sometimes thrown up dead or dying in great numbers on the beach. It is from eight inches to a foot long, and when caught in a pool by the receding tide it is very difficult to see, for it simulates closely the color of the sand. As it swims along it changes color almost instantly by a muscular action of the pigment cells covering the surface, so that from a dark brown creature it suddenly becomes gray, or yellow, or spotted, or nearly white. Its large eyes and sucker-bearing tentacles, which stick tightly when applied to the hand, are strange things, while its mouth is provided with two dark, horny jaws, like the beak of a parrot. I have found the jaws of two dozen squids in the stomach of one shearwater I shot off the end of Cape Ann, which goes to show not only the voracity of this bird but the plentifulness of squids.
Locomotion in the squid is generally backwards and swift by the forcible ejection of water from the interior of the mantle, but the animal can also propel itself forward by turning its siphon back, as well as by the propeller-like action of the tail. When much disturbed and desirous of escaping observation, it does not hide its head in the sand, as does the fabled ostrich, but it obscures its surroundings and itself by the ejection of an inky fluid.
The last sea-dweller to which I shall refer is one that would seem to belong to the lowest order of animals, or even to the group of vegetables, but it is in reality at the top of the invertebrate tree. I refer to the seasquirt, — that one called clavata, or “like to a club or knotty branch.” It is an orange-colored wrinkled affair about the size of a pullet’s egg, which squirts when touched. It is set on a long stem adorned with seaweed-like hydroids and is attached to stones in deep water. A winter’s storm is generally needed to tear these creatures from the bottom and throw them up on the beach. The warm-weather beach-combers rarely find them. The reason this singular animal, for such it is, is placed high up on the tree of invertebrate life is because in the larval stage it has the beginnings, so to speak, of a backbone — the notochord. Having advanced thus far it seems to despair, and degenerates in the adult stage into the soft, backboneless creature with vegetable tendencies we have just seen.
I am tempted to conclude this very inadequate, but I hope suggestive, survey of the lowly life of the seashore by an account of something which does not belong to this group of marine invertebrates, — something that in very truth is neither fish, flesh nor fowl, nor good red herring, and which, although I have looked for it these many years, I have never found. But I do not despair, and some day I hope to justify my beach-wanderings in the eyes of my more practical friends, by finding a fortune in the shape of a piece of ambergris. However, I do not let the subject weigh heavily on my mind, and even if I fail in my quest my beach-wanderings have paid me well in ways not dreamed of by those same commercial-minded ones. Ambergris, or gray amber, as its name would imply, is a gray, greasy substance which is formed as the result of disease in the intestines of the sperm whale, and, when cast out by the animal, floats on the surface of the water and may be thrown ashore on any beach. There are many curious theories as to its nature, and that by old Josselyn is not the most curious. He says in his “New-Englands Rarities:” “Now you must understand this Whale feeds upon Ambergreece, as is apparent, finding it in the Whales Maw in great quantity, but altered and excrementitious: I conceive that Ambergreece is no other than a kind of Mushroom growing at the bottom of some Seas; I was once shewed (by a Mariner) a piece of Ambergreece having a root to it like that of a land Mushroom, which the Whale breaking up, some scape his devouring Paunch, and is afterwards cast upon shore.”
It has been known to form masses weighing over two hundred pounds, and, as it is worth many dollars an ounce for the manufacture of perfumery, one can easily estimate that a fortune awaits the lucky finder of the larger pieces. The tale is told of the finding of a piece at sea by the master of a fishing schooner, who, ignorant of the true value of the substance, had it used for greasing the masts. On his return to port the value of the small portion remaining was recognized, and he sold it for two thousand dollars, yet he was a very unhappy and dissatisfied man! Life to him became one long regret!