Popular Science Monthly/Volume 35/July 1889/Sea-Butterflies
| SEA-BUTTERFLIES. |
By Prof. CARL VOGT.
THE little boat lay ready at the dock of Nice; I had at that time to depend upon my own hands. The idea that a permanent station could be established on the sea-coast, with laboratories in which the student could find in one place all the aids he would need in the investigation of sea-animals, had not yet occurred to any one. It was not till I had worked two years in Nice, and had suffered all the inconveniences and loss of time that come from deficiency of means, that I devised plans for building such an establishment, which all came to no result till Herr A. Dohrn, with unexampled energy, founded the zoological station in Naples, a model that has been imitated in nearly all coast countries.
Thirty years ago, we did the best we could. I was living in Nice in a private house, since turned into a hotel, which stood on a projecting rock. My fishing-ground was in the Bay of Villafranca, which, cutting deep into the shore a few kilometres to the eastward, was inexhaustibly rich in swimming creatures. I had come to an understanding with an intelligent fisherman. When the weather seemed favorable to the flowing of rich tides into the bay, Joacchino would come early in the morning to my house and tell me that the Graziella lay at the dock. Then he would pack two baskets with large, wide-mouthed glasses: I would stuff into my pockets as many small glasses as they would hold, and take a net made of the finest bolting-cloth stretched upon a copper ring, and furnished with a long, strong handle. Joacchino had a similar net of his own in the boat. Magnifying glasses and compasses, hung by ribbons from the neck, completed the outfit, which was quickly deposited in the boat; Joacchino rowed, for we only went out when the air was still, and I steered. In about an hour we were in the bay.
"Do you see the tide, Joacchino?"
"There, sir, before the Sanita," answered Joacchino, after having risen and looked around.
I saw, indeed, the clear streaks with smooth, unruffled surface that usually denote the coming in of the tide.
"I hardly think," I said, "that we shall fill our vessels to-day. It is getting cloudy, and the sun is not shining."
"So much the better, sir. The sirocco is blowing outside on the sea, and will come in here in the afternoon. Do you see the long swells on the tide which run from the offing along the coast to the back of the bay? I will wager that the stream reaches to the other side of the bay, over by the lighthouse, and from there to the mouth. . That is a good sign. The more cloudy the sky is, the more butterflies we shall catch."
"We must go out from the land to catch butterflies. We might perhaps get a few swallow-tails, mourning-cloaks, or a few pretty Jasons out there; but here—"
Joacchino somewhat nervously drove the boat by vigorous oar-strokes to the edge of the stream, which was really swarming with animals of various kinds.
While the Medusæ and the polyps had some attractions for him, he aimed particularly for a place where a transparent animal was making a fierce eddy in the stream. I at once recognized the indomitable creatures that turn so wildly in circles. It was a perfectly transparent Pterotrachea, about a span in length, as thick as one's finger, which keeps its long snout incessantly foraying around.
"Where you see them," said Joacchino, "the butterflies are not far off. There! you have a handsome one, of the largest kind" He handed me a glass, with which he had dipped some out of the water.
I am quite proud of young Joacchino. He has eyes like a lynx, and has learned that the more delicate animals must not be touched with a net, but must be let run in with the water into a glass held out to receive them. In deep water the net must be handled so as to cause an eddy by the side of the animal that shall draw it along on the surface.
"Bravo, Joacchino!" I said, after examining the animal in the glass. "I know now what you know about butterflies." The animals which have been named Pteropoda, or wing-footed, really deserve the name. They are excitable creatures, that fly round in the broad glass, often strike the walls in their vehement movements, then suddenly draw in their wings, turn downward, and slowly sink to the bottom, to spring up again after a time and begin the old play anew. I recognized at once the boat-butterfly, dedicated to the famous seaman Peron, the Cymbulia peroni (Fig. 1). A little way off, one sees merely the eddy in the water
Fig. 1.—Cymbulia peroni.
and a brownish kernel about the size of a grain of wheat; only on a closer inspection can we distinguish two large, roundish wings, as clear as glass, that sit upon a yellowish body drawn backward in length, that rests in a crystal boat, the contour of which can not be exactly discerned, because the substance of which it is formed has the same refractive power as water. It is only when the animal is put, hardly covered with water, in a flat saucer of glass, against a black ground, that we can see the figure of a boat hollowed above, rounded in front, and drawn out into two points behind (Fig. 1) the outer surface having wart-like processes, while fine points like the teeth of a saw rise from the upper edges in front of and behind the body.
The body itself lies in the upper hollow of the boat, and is so loosely fixed to it that if carelessly handled it is easily separated from the shell. The shell is made of a uniform and structureless substance, about midway in consistence between jelly and gristle. The animal does not appear to be especially affected in its motions by separation from the boat, but flies around in the water as before; but, as it does not live long in captivity, it has not been possible to determine whether or not it is able to form a new shell. It may be said, against such a supposition, that besides perfect animals, only empty shells or rarely shelless animals are found in the sea, while none have ever been observed with imperfect shells, as must have been the case did a new growth take place.
The body is very curiously constructed. Leaving out the wings, it appears insignificant in proportion to the shell, and as if buried in it. The fore-part corresponds with the thicker, bluntly rounded part of the boat. In the posterior channel plays a threadlike tail-appendage, starting from a heart-shaped, extremely thin, and transparent fin, which is attached to the body by a thicker stem. There is no head; in front, at the spot where the wings join in the central line, lies the mouth, projecting in the shape of a little round mast, behind which a dark-brown, crescent-shaped streak may be perceived. This is the pharynx-head shining through the body-cover. Like other mollusks, this animal bears a peculiar inner armament which has been wrongly named the tongue, but has not the least in common with the tongue of vertebrates. This tongue is variously formed, according to the food of the animal—like a file or rubber in plant-eaters, or provided with teeth, hooks, and thorns in carnivores. All the sea-butterflies have on their tongues rows of strong, pointed hooks; they are—perhaps with a few exceptions—distinctively carnivorous. But our fishing did not end with the capture of a few Cymbuliæ and slipping them into the glasses which we had provided, for inspection at home. The Cymbuliæ are the giants among the sea-butterflies of the Bay of Villafranca; a multitude of small fry also swim in the tide which even the most skilled eye can not distinguish from the water, so clear and transparent are they.
"Slowly, Joacchino! Let us drift with the stream!"
I sink the fine net into the water, so that its rim is barely under the surface, and set the long handle on the edge of the boat against the thole-pin. Joacchino slowly pushes the boat onward without beating the water.
"Stop! Give me the lager-beer glass!" Blessed be Gambrinus! Without his invention, nobody perhaps would have thought of furnishing beer-glasses with fixed handles. The net, which was filled with a mass of swimming creatures that could not escape, was raised above the water till there was room to dip out of it with a beer-glass. We have been fortunate, for we have fallen upon a swarm of needle-butterflies.
Fig. 2.—Tiedemannia.
Creseis acicula (Fig. 3), and have caught a considerable number of them in our glass, besides other shelled species, such as Hyalea tridentata (Fig. 4), and Cleodora lanceolata (Fig. 5). But it is best to isolate them, and to separate from among the other little transparent minnows certain crustaceans, some of which might take a notion to attack the butterflies and eat them. Then we turned toward home. The hour and a half occupied in the journey back was spent in selecting out.
I let the water run out of the net into a small glass, so as to be sure that it contains no other animals, and take a glass tube long enough easily to reach the bottom of the mug. The life here is all in a confusion of panic on account of the cramped quarters. I introduce the tube, holding the upper end tightly closed with my forefinger. The air contained within it permits very little water to enter.
We have now to keep a sharp lookout. When I perceive a butterfly which perhaps has sprung at a bound to the surface and is now gently sinking back, I try to bring the lower end of my tube close to it. My forefinger is then suddenly raised; a stream of water, stronger as the tube is deeper in, presses out the escaping air and draws the animal in with it. My forefinger is then brought down to close the upper end, the tube is drawn out, and the animal in it is transferred to the collecting-glass. This is a simple method of catching such small and delicate animals, but must be well practiced if one would acquire any skill in it. It can not be used successfully in a rough sea, and when that is the condition the student must wait till he gets home. But when the animal is secured, it is a real joy to lose one's self in contemplating it with the lens and microscope. The needle-butterflies are a beautiful object. Their cylindrical, glass-clear shell is firm enough to stand a slight pressure. An animal is caught in the prescribed way and put in a compressorium; a small instrument, a thin glass-plate or cover, is used with a tortuous movement to bring it closer up on the stand, which is also of glass. A drop of water is made to fall on the stand, the creature to be examined is brought up, and the two plates are twisted till both touch the drop. We might crush our specimen with the apparatus; but we carefully regulate the pressure so that no harm shall come to it while it is held fast in the same place. It struggles, beating with its wings, but all its exertions are in vain; it can not in the narrow space overcome the pressure that weighs upon its shell.
It is a wonderful view we get under the microscope of the fine muscular fibers crossing one another in the wings, now drawing together and now extending out, and we can follow the ramifications of the nerves and the vessels of the circulation. We perceive the motions of the mouth as it opens and shuts, the pharynx-head with the tongue, which is projected and withdrawn, the connections of the intestine; we see the heart beat, and can follow the current and eddies of water which are produced in the breathing pores and certain secretory openings by the beating of innumerable cilia in their regular way. The animals are hermaphrodite. We can see the eggs and other products in the organs where they are generated and in the channels through which they are expelled. Only a few hours passed before the needle-butterflies and their relatives could be seen laying eggs, with transparent shells, which resembled rosaries or long pods, in the spaces of which the eggs swam in a clear liquid. Do they lay these eggs because they are comfortable in the vessel, or in order to rid themselves of what is a burden in their straitened captivity? While this question is still unanswered, it is certain that such strings of eggs and pods are also found drifting in the open sea, that the eggs which are laid in captivity are usually fertilized, and that the development of the embryo can be followed under the microscope—at least, till the point when the larvæ, which go through many metamorphoses, leave the shells to swim in the sea. These do not resemble the parents, but the larvæ of creeping sea-mollusks, and swim by means of a ciliary apparatus which grows on the head, and afterward, when the wings have been formed, is repressed. The free larvæ have not been successfully raised any further in captivity. Probably they die of hunger, for it is impossible to feed them. But we can fish them out of the sea in a net, and can compare from the various forms found among them the succession of single steps in their growth to the adult state. This is, indeed, not always easy, for, on the one hand, the larvæ of different species are often very much alike, and, on the other hand, the currents do not always fetch what is wanted, so that many observers have to wait year after year to continue their observations and bring them to a conclusion.
Dealing with the pelagic animals that swim on the high sea is a delicate matter, and, despite the most careful researches, the
Fig. 3.—Creseis acicula. Fig. 4.—Hyalea tridentata. Fig. 5.—Cleodora lanceolata.
cause of their appearance and disappearance has never been ascertained. In the years from 1850 to 1852, which I spent in Nice, and when I fished with my fine net at least twice a week in the Bay of Villafranca, I only found a few species of needle-butterflies and related species. Cymbuliæ, which could not have escaped me then, I first found at a visit in the Easter vacation of 1867, when they were very numerous. Messina is the Mediterranean station where the butterflies are brought in the largest number and most various forms from the stream of Charybdis. When I last spring asked my colleague there. Prof. Kleinenberg, to send me a few specimens of a naked shelless species (Pneumodermon), my courteous friend sent me a goodly number of other butterflies, and wrote: "I am sorry I can not send Pneumodermon. While it was formerly so abundant that one could hardly make a haul without having some in his net, there are now none here." The same Job's comfort came from the zoölogical station at Naples, which usually afforded remarkably fine sea-animals, and where I myself had obtained Pneumodermon two years before. I received a splendid lot of other butterflies, which were so well preserved that one could almost believe they were still alive; but Pneumodermon was not among them.
In Messina, however, is found the round butterfly, Tiedemannia (Fig. 2), of gigantic proportions when compared with the others, which somewhat resembles the mourning-cloak of the land-snails.
Fig. 6.—Clinopsis Krohnii. Fig. 7.—Clione borealis. Fig. 8.—Limacina arctica.
but is otherwise of like structure with the Cymhuliæ. It also has a water-clear shell, but much smaller and entirely smooth; its wings are united into a large disk, and its mouth is drawn out into a long, double-tipped snout, which the animal carries in swimming like a rakish mast between the wings.
All the sea-butterflies mentioned above are predatory, but I am inclined to believe that certain gorbellies, which are comparable to corpulent night-moths, and might be called thick butterflies (Hyalæa), are also, besides, plant-eaters. They tumble around clumsily at Messina and Naples, are occasionally driven to Villafranca, and are distinguished by their swollen, brownish shell, extending into a point behind, and having a narrow opening, out of which rise the short and massive three-lobed wings. They usually bear ragged or ribbon-like appendages of a brown or dark-green color, which well adapt them to abiding among the seaweeds. In the intestines of many specimens which I have examined for that purpose I have found among fine grains of sand and mold dubious remains of sea-plants and little shells of swimming mollusk-larvæ.
Many sea-butterflies are naked, having their spindle-like bodies, instead of shells, covered only by a sack-like skin. The laterally fixed wings are sometimes drawn back into pockets, and over them rises a roundish, somewhat depressed head-part, which is occasionally provided with appendages bearing hooks or suckers. To them belongs the above-mentioned violet-colored Pneumodermon of the Mediterranean Sea, which, when danger is impending, envelops itself in a white cloud of slime that is secreted in numerous glands, but is soon exhausted.
A species occurs in the northern seas which, together with a little butterfly, Limacina arctica (Fig. 8)—a species having a somewhat spiral, transparent shell—comes into remarkable direct relations with man. The little Limacinas appear in immense swarms in the polar seas, and the not less numerous naked Cliones, Clione borealis (Fig. 7), which are much larger and inflict grievous destruction upon them. In the Mediterranean Sea the Cliones are represented by the related genus, Clinopsis Krohnii (Fig. 6). The polar voyager. Captain Halböll once tried to bring some living Cliones to Prof. Eschricht, in Copenhagen, for examination. Knowing that they were carnivorous, he fed them with reindeer meat, which they ate greedily at first; but, although he changed the water frequently, he was not able to keep them alive more than eight days, and had to bring them preserved in alcohol. But Eschricht made a very satisfactory research upon them.
The Limacinas eat little crustaceans, the Cliones eat the Limacinas, and both are consumed by the ton by whales. The Greenland whale appears to live almost exclusively on the two species of sea-butterfly, which it has to swallow in immense quantities to fill its capacious maw. It eats also other pelagic small fry and crustaceans as side-dishes.
These are only indirect relations in which the sea-butterflies inhabiting all seas stand to man. But they are important enough. Without whale-food, no whales; without these, no blubber to grease sailors' water-proof boots and overalls; and without boots and southwesters, no sailors and high-sea fishermen; and without whales, no whalebone, no parasols and umbrellas and corsets, which were not worn by the beauties of ancient times, because they were limited to the productions of the Mediterranean Sea, where there are no Greenland whales. But chains of this kind can be found everywhere.
The older French naturalists—D'Orbigny, Péron, Lesueur— who paid much more attention to the butterflies of the tropical seas than to those of the nearer Mediterranean, pronounced them nocturnal high-sea animals. They had never been seen near the coast, nor before sunset. They were not found at a less distance than about ten marine miles from the coast, and disappeared in the deep at daybreak. That may be correct for the tropical regions, where a dazzling sunlight is poured upon the highly heated surface of the sea; but it must not be forgotten that the sea-butterflies have no eyes, and their keeping away from the coast, where the water is highly warmed to a considerable depth, may indicate that temperature is more a determining factor in this behavior than light. The sea-butterflies behave differently in the Mediterranean. They are not wanting on sunny days, but are more numerous when the sky is clouded and in the night. In midsummer they are, like many other pelagic animals, extremely rare, and keep themselves in the great deeps. Prof, Chun, of Königsberg, who investigated this matter in the summer of 1886, fished larvae of Cymbulia and Tiedemannia from as great depths as a thousand metres. Temperature may also be the decisive moment in this case; why should the animals not spend their summer vacation there? The sea-butterflies of the Mediterranean are not at all afraid of the coast. The Bay of Villafranca is hardly two kilometres wide, and they swim in the straits and harbor of Messina, I have caught multitudes of needle-butterflies in the daytime in that stream, close by the shore.
The case is somewhat different in the polar seas. We hunt the whale during the polar summer, when the sun does not set for months, and not in the polar nights, which are also months long, and when the ships would be frozen in the ice. If the Cliones and Limacinas were night animals they would not come to the surface during the whaling season, and would also not be known to sailors and hunters. They might, in fact, seek the deep in winter for the same reasons that they resort to it in summer in the Mediterranean—to escape extremes of temperature. Everything that lives depends on external conditions, and, as these are not everywhere the same, the behavior of the organisms subject to them must adapt itself to the local relations.—Translated for the Popular Science Monthly from Land und Meer.
| FARM-LIFE IN CHINA. |
By ADELE M. FIELDE.
THE number of persons that may subsist upon the products of an acre of land appears to have been practically determined by the Chinese. On ground that has been tilled for thousands of years they, by a skillful use of fertilizers and by attention to the welfare of each plant, raise crops that would honor a virgin soil.
In this Swatow region probably nine tenths of the men are engaged in agriculture. The farmers live in villages, isolated dwellings being uncommon. The villages are walled, contain no wasted space, and are densely peopled. The wide-spreading, flat fields, lying along the river-banks at the foot of the hills, may be made to yield here on the Tropic of Cancer a constant series of crops without interval on account of winter. Their chief productions are rice, sugar-cane, sweet potatoes, pulse, garden vegetables, peanuts, indigo, sesamum, ginger, the grass-cloth plant, tobacco, and wheat. Rice is the staple food of the people, and in the best years the local product just supplies the local demand. Sugar is the principal export. The cane requires less labor than any other crop, and will grow upon unwatered land, which is unsuitable for rice-culture. One crop of cane or two crops of other produce may be grown in the same year upon unwatered land. On the best rice-fields three crops are sometimes raised. The early rice is sowed in April and harvested in July; the late rice is sowed in August and harvested in November, and the field is then sometimes planted with garden vegetables, which are pulled in March. The expense of fertilizing the third crop is so nearly equal to its value that it is never reckoned as a source of profit to the cultivator.
The. whole country belongs theoretically to its sovereign, and upon all land that can be tilled with profit a tax is paid into the imperial treasury. The sum due annually to the Government for the use of land is fixed for each field, amounts to from sixty cents to two dollars, and averages a dollar and a half upon each English acre.
When a father dies his land is divided equally among his sons, the eldest receiving an additional tenth on account of the extra expense to which he is put in worshiping the manes of the ancestor. The land is distributed very generally, though unequally, among the people, and is usually tilled by its peasant proprietor. Few own so much as two hundred acres; one who owns ten acres is reckoned wealthy, and he who owns one acre possesses a competence. Those who own from one tenth to one half an acre are