From the French of Dr. N. Joly.
From the remotest antiquity the red color sometimes observed in water appears to have attractged attention. In all ages there have been stories of rains of blood, and of rivers changed to blood, and these phenomena have given riseto the most ludicrous explanations, and to the most ridiculous apprehensions. In Exodus (vii., 20, 21), we read: "All the waters that were in the river were turned to blood. And there was blood throughout all the land of Egypt." Homer speaks of the dews of blood which preceded the Trojan War, and those which foreboded the death of Sarpedon, king of the Lycians. Pliny in his "Natural History" (book ii., c. xxxvi.) tells of a rain of milk and blood which fell at Rome in the consulship of M. Acilius and C. Portius. Finally, the historian Livy mentions a rain of blood which fell in the Forum Boarium. In times much nearer to our own, phenomena of this kind have been observed at various points in Europe, producing ridiculous alarms, and even leading to actual seditions.
The cause, or causes rather, of these so-called rains of blood are now well understood. Every one knows that they are to be attributed either to mineral particles diffused through the air strata which are traversed by the rain, or to the dejections of certain moths in their last metamorphosis, or to the remains of infusoria carried up by the winds. But the ignorant multitude continue still to believe in rains of blood, and bow down blindly before so-called miracles which have no existence save in the wild fancies of those who regard them as articles of faith.
Red water of the Salt-Marshes, taken from the surface.
The same after it has been allowed to rest. (The infusoria have risen to the surface. )
We are not concerned now with these errors and superstitions, on which modern science has pronounced its verdict; we propose rather to consider some well-attested facts, the causes of which leave no room for doubt or ambiquity. It is now ascertained beyond question that, where fresh water wears a peculiar tinge, this coloring is due to the presence of infusoria (Euglena viridis. E. sanguinea, Astasia hæmatodes), or to microscopic vegetation (Oscillatoria rubescens, Sphæroplea annulina), or to minute entomostraca (Daphnia pulex, Cyclops quadricornis).
The waters of the sea may also be tinged in a similar way. Thus, in 1820, Scoresby found that the blue or green tinge of the Greenland Sea was caused by an animalcule allied to the medusæ. Of these he counted 64 in a cubic inch; this would be in a cubic foot 110,392, and 23,888,000,000,000 in a cubic mile. According to Arago, the long and sharply-defined streaks of green in the polar seas include myriads of medusæ, whose yellow color, added to the bue of the water, produces green. Off Cape Palmas, on the Guinea coast, Captain Tuckey's ship appeared to be sailing through a milky sea. The cause of the phenomenon was the multitude of animals floating at the surface, and masking the natural tint of the water. The carmine-red streaks which various navigators have sailed through on the high-seas are produced in the same way. In 1844 Messrs. Turrel and Freycinet saw the Atlantic Ocean, off the coast of Portugal, of a deep-red color, owing to the presence of a microscopic plant of the genus Protococcus (P. Arlanticus). This color was duffysed over an area of no less than five square miles. M. Montagne, who has described the alga which produced this phenomenon, closes his memoir in these words: "When we reflect that, in order to cover one square millimetre (0.03937 inch), we must have 40,000 individuals of this microscopic alga, we are filled with amazement on comparing the immensity of such a phenomenon with the minuteness of the cause which produces it."
Monas Dunalii Magnified. a. Very young individuals, colorless. b. Individuals not yet full grown, colored green. c. Adults very deep red. d. Adults of lighter red.
Monas Dunalii, dead, and of globular shape.
As for the waters of the Red Sea, the periodic reddening which distinguishes them is caused by the presence of a confervoid alga which naturalists have called Trichodesmium erythræum. Finally, Pallas tells of lake in Russia, called Malinovoé-Ozéro, or Raspberry lake, because its briny water and the salt made from it are red, and have the odor of Violets.
The coloration of the Mediterranean salt-marshes, a phenomenon long known to the salt-makers of Languedoc, but first studied by savants in 1836, and by me in 1839, has also been explained in various ways more or less near the truth. 1 The sauniers (salt-makers) of Languedoc give the names of tables, partennements, and Pièces maîtresses to the various compartments into which the sea-water is passed as it arrives at different degrees of salinity.Messrs. Audouin, Dumas, and Payen, of the Institute, have attributed it to the Artimia salina, a minute branchiopod crustacean, which in fact swarms in the Partennements1, where the saltness of water is far below the degree of saturation requisite for the precipitation of salt crystals, but is of much rarer occurrence where the water, being very highly concentrated, assumes at times a blood-red color. Messrs. A. de Saint-Hilaire and Turpin have supposed the real cause of this strange coloration to be certain microscopic plants, of very simple organization, which they call Protococcus sanguineus ans Hæmatococcus kermesinus. This, too, was the opinion of M. F. Dunal, who had studied the rubefaction of the water of our salt-marshes before St. Hilaire and Turpin. As I was at that time employed in teaching Natural History in the Royal College of Montpellier, where I had among my pupils several youths who have since become distinguished masters themselves (Louis Figuier, Amédée Courty, and Henri Marès, for instance), I too had a desire to study the curious phenomenon of the reddening of water, and to this end I visited the salt-works of Villeneuve, two or three miles distant from Montpellier. The water there was then of a very decided red color. I collected on the spot some samples of the water which looked most like blood, and also of water which, being less briny than this, was also of a fainter red color. Under the microscope the water collected in the various compartments exhibited myriads of minute creatures, with oval or oblong bodies, often compressed in the middle, but sometimes cylindrical. Very young individuals were colorless, those a little older were greenish, and the adult were of a deep red. The mouth had the form of a conical prolongation, and was retractile; they were eyeless, and the stomach and anus could not be clearly made out.
Dead Monads, colorless.
Part of the Digestive Tube of Artemia Salina, in which are seen (a, a) dead but not digested monads, and (b, b) cubical salt-crystals.
With a high-power microscope I was able to see in the anterior part of these supposed protococci two long, flagelliform, and perfectly transparent processes which they kept in rapid motion, and by means of which they swam about in the drop of liquid spread out on the slide of my instrument. There was no longer room for doubt. The protococci and hæmatococci of Messrs. Dunal, St.-Hilaire, and Turpin, were animals - true monads, and I gave them the name of Monas Dunalii, in honor of my preceptor, Prof. Dunal. He was the first to suspect the true cause of the red color of the Mediterranean salt-marshes; but he had only an indistinct insight into the matter. He examined the animalcules only after they were dead, that is, at the moment when they had become globular and motionless, like protococci; and his specimens were dead, because he had filled his vials up to the brim with the water, and then sealed them hermetically. But these little animals must, above all things, have free respiration. Accumulated in immense numbers in a very small quantity of water, with the outer air entirely excluded, they all died while being carried from Villeneuve to Montpellier. They were then taken for protococci, being motionledd and globular. I took precautions against committing this mistake, by only half filling my specimen-tubes, and, better still, by examining the water of the salines on the spot.
Artemia Salina (adult) natural size, and highly magnified. o. Median eye. y,y. Pdunculate eyes. a,e. Antennæ p. Incubatory pouch with eggs. ab.Abdomen. ap. Tail-shaped appendages. c. Digestive tube.
It is a remarkable fact in the history of the Monas Dunalii that, like the Protococcus nivalis, which gives to the snow of the polar regions now a green tinge, anon a red, this animalcule presents, when young, a green tinge, which changes later to brick-red, and then to blood-red.
The degree of concentration of the water has a marked influence on them. On the 1st Octoberm 1839, after the driest summer on record, the liquid in the tables indicated 25° salinity in Baumé's areometer, and it was of so deep a color as to stain a corner of my pecket-handkerchief a blood-red. On October 28th, after twenty-eight days of steady rain, the water in the pièces maìtresses, instead of presenting a purple color, as on the first day of the month, resembled blood with a very large amount of serum, and the monads in it were less numerous, and of a lighter red, although the water was still of 20° salinity.
Finally, we must not omit to state that the monads are very sensitive to light, which they seek with a certain degree of avidity. This may be easily seen by putting a number of these infusoria into a flask two-thirds filled with sea-water. Soon they will be seen to rise to the surface of the liquid, and to crowd together on the side where the light is strongest. If the flask be turned about so as to bring them on the darker side, they soon take their former position again. We must also observe that these animalcules sometimes go sown to the bottom of the tables, and then the coloration of the surface grows fainter, or entirely disappears.
From all this it follows that the red color of the Mediterranean salt-marshes is caused by the Monas Dunalii; but is that animalcule the only cause of the phenomenin? Has not the Artemia salina of Audouin, Dumas, and Payen, also something to do with it? This problem was soon solved. We have first to bear in mind that these little crustaceans are found in far greater numbers in brackish water than in water at its maximum point of concentration, and that in the latter case, indeed, they occur so rarely that their presence may be regarded as in some sort merely accidental. In water of this kind, the artemia appears to be sickly; it evidently languishes in the over-dense medium; it swims about with difficulty, always keeping at the surface. It is more or less of a red color along the line of its digestive canal; but this coloration is secondary thing, and is owing to the monads it has swallowed in water. The latter deposits in their intestine salt-crystals, which may be seen through their transparent envelope, mingled with monads in a state of partial or total digestion.
Far, then, from being the cause of the purple tint of salt-water in its last stage of concentration, the artemia is indebted for its accidental coloring to the Monades Dunalii it takes into its digestive canal, or which settle among the filaments of its branchial feet. This I have demonstrated by keeping colorless artemiæ for a while in water tinged by red monads, or simply by carmine, and so giving them a red color.
But, though the artemia has nothing to do with the coloration of water, it is, nevertheless, a subject of wonder and study for the physiologist. Like several other animals belonging to the great sub-kingdom Articulata (psyche, bee, silk-worm moth), out crustaceans possess the singular privilege of reproducing themselves without being subjectted to the general law of sexual union. Among several thousand artemiæ studied by me, I have not found a single well-defined male individual. The distinguished Genevan naturalist, Carl Vogt, said, the other day, that he had had the like experience. Hence we may conclude that the artemia of our salt-marshes perpetuates its kind by means of virgin females, whose eggs, although deprived of seminal impregnation, are developed in an incubatory sac situated at the base of the maternal abdomen. These produce young artemiæ, which have to undergo amazing metamorphoses before they arrive at a complete resemblance to their parent. The name of parthenogenesis has been bestowed on this singular mode of reproduction by virgin females, independently of commerce with males; oftentimes, the latter do not exist at all, or at least are as yet unknown. In conclusion, we would remark that the eggs of our virgin artemia produce only females, while the unfecundated eggs of the queen-bee produce males, and males only.
- La Nature.
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