The Leeuwenhoek lecture, 1965. Some controversial aspects of bacterial sexuality.

Abstract

'I must say to you, as I’ve oft-times said already, that ’tis not my intention to stick stubbornly to my opinions, but as soon as people urge against them any reasonable objections, whereof I can form a just idea, I’ll give mine up, and go over to the other side.’ (A. van Leeuwenhoek: see Letter 81, 19 March 1694.) As these words of his testify, Antony van Leeuwenhoek had a very forthright and truly scientific attitude to controversy. Born 333 years ago this year, in the same year as John Locke, Christopher Wren and Jan Vermeer, there can have been few men, if indeed any in the history of science, whose observations and ideas were more in advance of the general knowledge of their times. In his hundreds of letters, over a period of fifty years to this Society, of which he was a Fellow, he unfolded the existence of a new and undreamt-of world of living creatures which ranged in size as far below the limit of unaided vision as the largest mammals extended above it. In fact, by his own computation, a thousand million of the smallest of his little creatures, the bacteria, were no bigger than a coarse grain of sand (Letter 33, to R. Hooke, 12 November 1680). Not only was he the first man to see bacteria, with lenses and microscopes made with his own hands, but he described virtually all the morphological varieties of bacteria that we recognize today. However, Leeuwenhoek’s lasting contributions to knowledge go far beyond his discovery of protozoa and bacteria. He carried out researches on red blood cells, which he accurately measured and often used as a standard of size; not only this, but he also observed their movement through the capillaries, thus completing the story of the circulation of the blood, established earlier by his contemporary, William Harvey. His comparative observations on his own spermatozoa and those of animals and his understanding of their role in procreation led him to speculate imaginatively, if somewhat wildly and erroneously, on the mechanism of fertilization and inheritance.