Surriray discovered the noctiluca while investigating the cause of phosphorescence of sea water at Havre, where it was abundant in the basins; sometimes in such abundance as to form a crust on the surface of the water of considerable thickness. "This singular little creature," says M. Frédol, "offers here and there in its interior certain granules, probably germs, and also luminous points, which appear and disappear with great rapidity—the least agitation determining their lustre." The noctiluca are so abundant in the Mediterranean and in some parts of the channel, that in a cubic foot of sea water, which has been rendered phosphorescent by their presence, it is calculated that there exist about twenty-five thousand.
Infusoria.
With the Infusoria we return to the domain of the infinitely little. Of this very interesting group a large proportion are marine, and numerous varieties of them are found in British seas. In their minuteness and variety they almost baffle the attempts of naturalists to classify them.
The waters, both fresh and salt, are inhabited by legions of active, ever-moving beings, of dimensions so small as to be inappreciable to the naked eye; these minute creatures are disseminated by millions and thousands of millions in the great deep, and all knowledge of them would have escaped us, as they escaped the knowledge of the ancients, but for the discovery of the microscope, the sixth sense of man, as it has been happily expressed by the historian and poet Michelet. Another writer of equally poetical mind, M. Frédol, tells us that "the infusorial animalcules are so small that a drop of water may contain them in many millions. They exist in all waters, the fresh as well as the salt, the cold as well as the hot. The great rivers are continually discharging them in vast quantities into the sea."
The Ganges transports them in the course of one year in masses equal to six or eight times the size of the great pyramid of Egypt. Among these animalcules, according to Ehrenberg, we may reckon seventy-one different species.
The water collected in vases between the Philippine and the Marianne Isles at the depth of twenty-two thousand feet (making some allowance for erroneous soundings), have yielded a hundred and sixteen species. Near the Poles, where beings of higher organization could not exist, the Infusoria are still met with in myriads; those which were observed in the Antarctic Seas, during the voyages of Captain Sir James Ross, offer a richness of organization, often accompanied by elegance of form, quite unknown in more northern regions. In the residuum of the blocks of ice floating about in latitude seventy-eight degrees ten minutes, nearly fifty different species were found. Many of them had ovaries, according to Ehrenberg, still green, which proved that they had struggled successfully with the rigours of the climate in searching for food.
At a depth in the sea which exceeds the height of the loftiest mountain, Humboldt asserts that each bed of water is animated by an innumerable phalanx of inhabitants imperceptible to the human eye. These microscopic creatures are, in short, the smallest and the most numerous creations in Nature. They constitute with human beings one of the wheels of that very complicated machine, the globe. They are in the rank and at the station willed for them, as determined in the great First Thought. Suppress these microscopic beings, and the world would be incomplete. It was said, and wisely said, long, long ago, "there is nothing so small to the view but that it may become great by reflection."
The Infusoria, in short, abound everywhere. We find their remains on the loftiest mountain ridges, and in the profoundest depths of the sea. They increase and multiply alike under the Equator, and towards the polar regions. The seas, rivers, ponds—the flower vase which rests upon the casement—even our tissues, and the fluids of our bodies—all contain infusorial animalcules. Whole beds of strata, often many feet thick, and covering a surface of considerable extent, are almost exclusively formed of their accumulated débris. It is to the Infusoria that the mud of the Nile and other fluviatile and lacustrine deposits owe their prodigious fertility. To them also is due the red or green layer of colouring matter found in ponds and tanks at certain seasons. When exposed to great solar heat, in order to extract the salt, as it is in the vast artificial basins hollowed out for the purpose in the salt marshes near the sea-shore in the south of France, the salt water, when it reaches a certain degree of concentration, acquires a fine rose colour, which is due to the presence of innumerable masses of small Infusoria having a reddish shell. Finally, let us add that the solid débris of certain fossil Infusoria, of surprising minuteness, have formed the stone so much used by workers in metal, which is known as tripoli.
The study of these creatures is intensely interesting to the naturalist, the philosopher, the physician, and the general reader. They have had a great part assigned to them in Nature, as is evident in the formation of certain beds of rock of immense extent, in which the geologist traces their action.
Our earliest knowledge of the Infusoria is traceable to the seventeenth century; to the celebrated naturalist, Leuwenhoek, we are indebted for their discovery. On the 24th of April, 1676, this observer saw for the first time some infusorial animalcules. Fifty years later, Baker and Trembley studied them anew. In 1752, Hill essayed the first attempt at their classification. In 1764, Wiesberg gave them the name of Infusoria, because he found them in such great abundance in animal and vegetable infusions. Müller published a special book upon them.