Leeuwenhoek, ANTON VAN

Leeuwenhoek, ANTON VAN, one of the most successful pioneer microscopists, was born at Delft on 24th October 1632, enthusiastically pursued microscopic work with self-made instruments in 1654, made many important discoveries, and died at Delft on 27th August 1723. He supplemented Harvey's discovery of the circulation of the blood by tracing the capillaries in the frog's foot, defined the red blood-corpuscles of Vertebrates, was the first to notice definitely what are now called unicellular organisms, and corroborated, though with erroneous interpretation, the discovery of male elements or spermatozoa by his student Ludwig Hamm. His investigations of minute structure led him to detect the fibres of the lens, the fibrils and striping of muscle, the structure of ivory and hair, the scales of the epidermis, the distinctive characters of Rotifers, and many interesting histo- logical facts in regard to insects. Much of his time and attention was given to a long series of investigations into spontaneous generation, of which theory he was a decided opponent. In the course of these studies he ascertained and proved, amongst other results, that oak-galls are primarily caused by the development of an insect's egg deposited in the bark; that weevils are hatched, not from wheat, but from an insect's eggs deposited in wheat; that the flea is propagated in a similar manner to other insects, not originated from dust, or sand, or the dung of pigeons, as was commonly believed; that Aphides are viviparous; that eels, instead of being produced from dew, are likewise viviparous; and that mussels are not generated from mud or sand, but from spawn. He also extended his inquiries to the growth of trees, and showed the differences that exist in the structure of the stem of monocotyledons and dicotyledons. The greater part of his discoveries and investigations were described in papers (112) contributed to the Philosophical Transactions of the Royal Society and papers (26) printed in the Memoirs of the Paris Academy of Sciences, of both which bodies Leeuwenhoek was a member. The most complete collection of his Works appeared at Leyden in 4 vols. in 1719-22. A selection of these was translated into English by S. Hoole (2 vols. Lond. 1798-1801). See the Life in Dutch by Haaxman (Leyden, 1875).