And finally, that these microscopic organic bodies are multiplied and enlarged by solitary reproduction without sexual intercourse till they acquire greater perfection or new properties. Lewenhoek observed in rain-water which had stood a few days, the smallest scarcely visible microscopic animalcules, and in a few more days he observed others eight times as large; English Encyclop. Art. Animalcule.

Conclusion.

There is therefore no absurdity in believing that the most simple animals and vegetables may be produced by the congress of the parts of decomposing organic matter, without what can properly be termed generation, as the genus did not previously exist; which accounts for the endless varieties, as well as for the immense numbers of microscopic animals.

The green vegetable matter of Dr. Priestley, which is universally produced in stagnant water, and the mucor, or mouldiness, which is seen on the surface of all putrid vegetable and animal matter, have probably no parents, but a spontaneous origin from the congress of the decomposing organic particles, and afterwards propagate themselves. Some other fungi, as those growing in close wine-vaults, or others which arise from decaying trees, or rotten timber, may perhaps be owing to a similar spontaneous production, and not previously exist as perfect organic beings in the juices of the wood, as some have supposed. In the same manner it would seem, that the common esculent mushroom is produced from horse dung at any time and in any place, as is the common practice of many gardeners; Kennedy on Gardening.

Appendix.

The knowledge of microscopic animals is still in its infancy: those already known are arranged by Mr. Muller into the following classes; but it is probable, that many more classes, as well as innumerable individuals, may be discovered by improvements of the microscope, as Mr. Herschell has discovered so many thousand stars, which were before invisible, by improvements of the telescope.

Mr. Muller's classes consist of

  1. 1. Monas: Punctiformis. A mere point.
  2. 2. Proteus: Mutabilis. Mutable.
  3. 3. Volvox: Sphæricum. Spherical.
  4. 4. Enchelis: Cylindracea. Cylindrical.
  5. 5. Vibrio: Elongatum. Long.
  6. *Membranaceous.
  7. 6. Cyclidium: Ovale. Oval.
  8. 7. Paramecium: Oblongum. Oblong.
  9. 8. Kolpoda: Sinuatum. Sinuous.
  10. 9. Gonium: Angulatum. With angles.
  11. 10. Bursaria. Hollow like a purse.