In common with most Hermit Crabs, this species, Pagurus pollicaris, lives in a shell which was formerly occupied by a univalve mollusk. The hind body of the Hermit Crab is soft and defenseless, and it is of necessity that the animal uses a borrowed covering. This shell is at once a garment and a home. It is, however, an abode which is always carried on the crab's travels. In the mating season they often travel together in pairs, the male sometimes with his great claw grasping firmly the female's front leg so that no rival may steal her. brings me to consider that most familiar, yet most mysterious, of all the creatures connected in the popular mind with the seashore-Limulus, the Horseshoe Crab (see Color Plate I). And who has not seen or heard of Limulus? There are few known species, but the number of individuals is legion. One species, X. polyphemus, is an American form; another, X. moluccanus, occurs only on the eastern coast of Asia. Our Limulus lives on sandy and muddy shores, below the low-tide mark, and it ranges the Atlantic coast from Maine to Yucatan. Incredible as it may seem in a creature so like the animals from which it derives its common name, the Horseshoe Crab is not a crab. It is not even a crustacean, if we are to believe the evidence of embryology and fossil-bearing rocks. It is supposed by some that it belongs with the spiders and the scorpions; the truth seems to be, however, that its nearest relatives died out ages ago. The young of the Horseshoe Crab are frequently found in great numbers on the less-exposed floor of tide pools and mud flats, where, molelike, they plow their tortuous trails through the bottom in pursuit of food (see page 56). The adult, when fully grown, attains an over-all length of two and a half feet; its domelike fore body is nearly a foot wide. Attached to the dome is the doubletipped hind body, somewhat flattened and of one rigid piece. This region of the adult's body is really the fused unit of what in the larval stage was a region of separate segments. Almost half the length of the Horseshoe Crab is taken up by the spinelike tail, which is literally hinged to the abdominal shell. THE HORSESHOE CRAB HAS EYES WHICH DO NOT SEE Besides the great compound eyes borne by the head, it has a pair of simple eyes, located one on each side of the base of the front middle spine. It is doubtful whether they are of any use to the animal; in fact, it is not improbable that, even with its compound eyes, the vision of the Horseshoe Crab is quite crude at best. The eggs spawned by the female number upward of ten thousand, nearly enough to fill a half-pint jar. These are greenish blue, transparent, spherical bodies about at of time at which development takes place depends on temperature and to some extent on light. By keeping the eggs in a dark, cool place, hatching may be retarded a year. Normally the eggs hatch about a month after they are laid. But before the actual hatching many interesting changes take place within the egg. The little larva soon forms after the egg is laid and continuously revolves within the shell. It assumes the so-called trilobite stage; then comes the first molt of its integument. Increasing growth has caused the contained creature to outlive its old skin and to cast it off within the egg case. By the time the tiny beast is ready to hatch, it is plump, possessed of two pairs of eyes, simple and compound, and has attained a general likeness to the adult. The exertions of the larva rupture the egg membrane, and the young animal is liberated. It is now a trifle more than a tenth of an inch long and a little less than this in breadth. Forthwith it shows great activity, striking out at once into the water and essaying to swim; but at this business it is a poor performer. It manages somehow to live a nomadic life for about a fortnight, being drifted about rather than getting anywhere of its own accord. Then it molts again and settles to the floor. With this molting it loses entirely all traces of its early form, some of which had been retained. A short, spinelike tail now graces the hind body, which is flat, and its whole underside is hollow (see page 61). Turning the animal upon its back reveals some of its most singular structural features. On first examination, the underside appears to present a confusing. array of appendages, but these are simpler than they seem. In the cavity of the head region are six pairs of legs with claws, the rearmost pair having, in addition to claws, some leaflike expansions which enable the animal to push itself through the sand and mud. Covering the abdomen are the gills, flat structures superficially resembling the leaves of a book. THE ONLY CREATURE THAT CHEWS ITS FOOD WITH ITS LEGS And here is an extraordinary feature which cannot fail to impress the most This fine specimen of the largest of all crustaceans, the Giant Spider Crab, Macrocheira kämpferi, measures nearly 12 feet between the tips of its outstretched claws. This animal is known to occur to a depth of over 2,000 feet in the seas off the coast of Japan. casual observer, for in no other living animal is there a similar adaptation serving the same purpose-the Horseshoe Crab literally chews its food with its legs, the base of four of these members being set with bristling spines, which act like jaws and with which the food is torn and reduced before it is swallowed. Notwithstanding the fact that these remarkable survivors from another day are still numerous enough to be among the commonest animals of the seashore, they are probably passing through their final period. In recent years, since mankind became aware of their destructive habits on oyster beds and value as a soil fertilizer, wholesale slaughter has taken place. Naturalists record that as late as 1856 more than a million Horseshoe Crabs could be seen to come ashore and lay their eggs within the area of a single mile along certain sections of our Eastern coast. To-day there is no such abundance, and at the present rate of decrease these curious creatures may become practically extinct within the time of men now living. In the Homeward Wake of Lewis and Clark, a Folding Steel Skiff Bears Its Lone Pilot on a 2,000-Mile Cruise on the Yellowstone-Missouri BY LEWIS R. FREEMAN AUTHOR OF "SURVEYING THE GRAND CANYON OF THE COLORADO" AND "THE MOTHER Of Rivers," DEAS as well as boats ride on rivers. Fur traders, gold seekers, Indian fighters-once this Big Muddy ferried them. The voyageurs dragging their clumsy, heavy-laden craft, covered wagons, and pioneer farmers fighting their hard way to free lands; Custer facing the Sioux that fatal day on the Little Horn; Buffalo Bill shooting meat for railroad builders-the ancient river saw them all come to impose the white man's culture. Now schools and colleges rise where Lewis and Clark pitched their rude camps; and radio music crackles where once echoed only the war whoops of the painted savage, the howl of wolves, and the grunt of stampeding buffalo. Long I had dreamed of this trip down the Big Muddy, in the path of Lewis and Clark, first white men to trace the course of this winding yellow stream. I wanted to see the places where they camped; to find the changes from ideas carried on the river since they came, saw, and wrote their quaintly worded journals. THE YELLOWSTONE IS THE MISSOURI'S MAIN FORK Livingston, Montana, on the Yellowstone, was my starting point; for to me, as to many old river skippers, the Yellowstone River is, despite confusing nomenclature, the main fork and chief source of the Missouri. Running north 50 miles from Yellowstone Park, this swift stream breaks from the mountain wall of the Rockies and flows northeast to join the Missouri. It was near here that Captain Clark, temporarily separated from Lewis on their return from the Columbia, first saw the upper Yellowstone. Livingston was in gloom. Lately the river had claimed three men. I, myself, should have a guide, at least for the first few miles, people insisted; for this upper Yellowstone has ways of its own; one cannot fathom its tricks by things learned on other rivers. Though my boat was of light steel, made to be folded and carried on the running board of an automobile, I had to admit an extra man might be useful in case I should swamp and need help to salvage my outfit. So word was sent upstream to "Buckskin Jim" Cutler, asking him to join me. He started down the river on a raft; but just as he reached Livingston a hanging tree swept him overboard. The eddies were too strong and he was drowned. Then Pete Holt, local chief of police and once my companion on a ski trip through Yellowstone Park, agreed to go with me for the first 100 miles. From the river bank groups of people waved farewell and shouted warnings to us as we shoved off, soon after breakfast, on the last day of June. Here the current was relentless in its onward urge. It is the almost complete absence of slack water between Gardiner and Glendive that makes the Yellowstone different from any other river of my experience. It is this condition, also, which makes it so nearly ideal for downstream boating. THE SKIFF BEHAVES WELL IN ROUGH WATER My skiff behaved so well in the first riffles that I was tempted to give it a baptism in the first really rough water, if I could find such a spot where salvage would be fairly easy in case of an upset. Such a chance came at the Springdale Bridge rapids, rated the worst on the river below Yankee Jim's Canyon. Here I gave the boat her head and let the undercurrent draw her fairly into the main J. E. Haynes VERY HORIZON Thousands upon thousands of these great creatures were killed for hides alone. Plains Indians, seeing their meat supply threatened by white hunters, however, and this herd is a part of the 1,000 animals that now find sanctuary string of rollers. Wild, wallowing water it was! But she took it like a duck. I felt supreme faith now in my new boat. Afternoon came, and we passed Buckskin Jim's raft stranded on a bar. A few miles below, we saw a dead man, one of the three drowned the week be fore at Livingstongrim evidence of the river's power. Here Holt left me. From there on to St. Louis, nearly two months away, I paddled alone. Sinister thunder, rumbling and persist ent, threatened me early next morning. Restless countermarching clouds above the valley were full of wind gusts. Sudden side swipes of air made the skiff yaw crazily. I kept going; but was yet to learn proper respect for Montana thunder storms! I had not yet come to the point where Clark had launched his dugouts. Seeking suitable timber, he had skirted the north bank all the way down from where he had first hit the upper Yellowstone (see text, page 73). The flint-paved mesas wore down the hoofs of his Indian ponies. so he had to protect them with buffalo-hide shoes. This increased his anxiety to take to the river. Near here, Clark says, one of his men, Gibson, in mounting within that reservation. |