96 THE HARMONIES OF NATURE. 



chiefly remarkable by the peculiar animal-like movements which 

 they exhibit. If a piece of the stratum of an Oscillatoria be placed 

 in a vessel of water, and allowed to remain there for some 

 hours, its edge will first become fringed with filaments, radi- 

 ating as from a central point, with their tips outwards. These 

 filaments, by their constant oscillatory movements, are con- 

 tinually loosened from their hold on the stratum, cast into the 

 water, and at the same time propelled forward ; and as the oscil- 

 lation continues after the filament has left its nest, the little 

 swimmer gradually moves along, till it not only reaches the 

 edge of the vessel, but often, as if in the attempt to escape con- 

 finement, continues its voyage up the sides, till it is stopped by 

 dryness. Thus in a very short time a small piece of Oscilla- 

 toria will spread itself over a large vessel of water. This 

 rhythmical movement, impelling the filaments in an undeviating 

 onward movement, is evidently of a nature very different 

 from the truly spontaneous movements of animals, and must 

 be considered simply as the expression of certain vital changes 

 taking place in the interior of the cells. 



The Oscillatoria3 are commonly of some shade of green, but 

 not unfrequently they are of a purplish hue, and sometimes so 

 dark as, when in mass, to seem nearly black. They frequently 

 form green scums on the surface of stagnant pools, but they 

 also occur in salt waters, and sometimes in such incredible quan- 

 tities that Professor Mayen once saw the ocean covered with 

 them over a space of seven hundred miles. The water swarmed 

 with small bodies of a stellar shape like snow flakes, which, on 

 being examined through the microscope, were found to consist 

 of bundles of Cscillatoria3. 



Among the marvels of microscopic vegetation, the Volv ox 

 globator, or ( globe animalcule,' as it has been called, from a 

 false idea of its nature, holds a conspicuous rank on account 

 both of the animalcule-like activity of its movements, and of 

 the great beauty and regularity of its form. Attaining a dia- 

 meter of -gL- of an inch, it may be seen with the naked eye, 

 when the drop containing it is held up to the light, swimming 

 through the water which it inhabits. Its onward motion is 

 usually of a rolling kind, but it sometimes glides smoothly 

 along without turning on its axis ; whilst sometimes, again, it 

 rotates like a top, without changing its position, so that it might 



