Illustrated plate depicting Antoni van Leeuwenhoek's (1632-1723) microscopic studies of frog and fish specimens.

Fig. 1: Frog embryo

Fig. 2: Later development of frog embryo

Fig. 3: Further development of frog embryo into tadpole

Fig. 4: Later development of tadpole

Fig. 5: Circulation of blood in the arteries of the tail of the tadpole

Fig. 6A: Arteries and veins in the tail of a tadpole

Fig. 6B: Aorta branch in tadpole

Figs. 7 & 8: Little fish

Fig. 9: Little fish under magnification

Fig. 10: Circulation of blood in the tail of the fish depicted in figure 9

In this pioneering work on microscopy, engraved plates detail the physiology of natural history specimens. Known as the "Father of Microbiology," van Leeuwenhoek is considered one of the first microscopists and microbiologists. After writing numerous letters to the Society regarding his scientific findings, van Leeuwenhoek finally was elected to the Royal Society of London in 1680 in spite of their earlier skepticism of his research. His work with the microscope revealed microbes, which he referred to as animalcules, and are now known as unicellular organisms.