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.